Conference Proceedings

To date, 68 articles have been published in conference proceedings. They are listed below in reverse chronological order.

2023
Title
Effects of the rhombohedral distortion in LaAlO3 on the quadrupolar splitting of the implanted 8Li+ NMR
Author
V. L. Karner, A. Chatzichristos, D. Fujimoto, R. F. Kiefl, C. D. P. Levy, R. Li, R. M. L. McFadden, G. D. Morris, M. R. Pearson, J. O. Ticknor, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012058
Year
2023
Abstract
We report the β-detected NMR of implanted 8Li+ in the rhombohedrally distorted perovskite LaAlO3. As observed in other insulating perovskites, the resonance has large quadrupolar splitting. However, it exhibits additional splitting due to the rhombohedral distortion. In addition, the magnitude of the electric field gradient at the 8Li site is larger than in cubic perovskites, such as SrTiO3, with vQ ≈ 191.3 kHz.
10.1088/1742-6596/2462/1/012058
Title
8Li βNMR studies of epitaxial thin films of the 3D topological Dirac semimetal Sr3SnO
Author
W. A. MacFarlane, M. Oudah, R. M. L. McFadden, D. Huang, A. C. Chatzichristos, D. Fujimoto, V. L. Karner, R. F. Kiefl, C. D. P. Levy, R. Li, I. McKenzie, G. D. Morris, M. R. Pearson, M. Stachura, J. O. Ticknor, E. Thoeng, H. Nakamura, H. Takagi
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012057
Year
2023
Abstract
The inverse perovskite Sr3SnO is a 3D cubic Dirac semimetal with a very small energy gap. Its unusual electronic structure confers a variety of novel properties, such as chiral topological surface states, and very strong itinerant electron orbital magnetism. Remarkably, when doped it also becomes superconducting. In the lowest carrier density samples, the Fermi level lies close to the Dirac points, and orbital magnetism is maximal. Here we report the results of ion-implanted 8Li+ βNMR in Au-capped epitaxial thin films of Sr3SnO as a function of carrier content. In addition, we stop the 8Li in the Au overlayer to seek proximal evidence of the chiral surface state. In high magnetic field (6.55 T), we find remarkably little contrast in spin-lattice relaxation (SLR) between low carrier density Sr3SnO and the Au overlayer. In the inverse perovskite layer, 1/T1 ~ 0.14 s-1, slightly faster than Au at 300 K, while in the overlayer, there is a small but systematic enhancement in 1/T1 compared to a control film of Au. The resonance in the Sr3SnO layer is broad with a long tail towards negative shift without resolved quadrupolar splitting.
10.1088/1742-6596/2462/1/012057
Title
8Li spin relaxation as a probe of the modification of molecular dynamics by inelastic deformation of glassy polystyrene
Author
D. Fujimoto, O. Brazil, W. C. Oliver, M. F. Jadidi, A. Sinnott, I. McKenzie, A. Chatzichristos, M. H. Dehn, V. L. Karner, R. F. Kiefl, C. D. P. Levy, R. Li, R. M. L. McFadden, G. D. Morris, M. R. Pearson, M. Stachura, J. O. Ticknor, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012053
Year
2023
Abstract
In our prior work, we showed that β-detected nuclear magnetic resonance (β-NMR) was a good probe of bulk room temperature ionic liquid (RTIL) dynamics and dynamic heterogeneity. We now investigate how the surface modifies these properties, presenting the first depth-resolved β-NMR measurements in 1-ethyl-3-methylimidazolium acetate as a liquid, supercooled liquid, and glass. This interfacial region is important for understanding how constrained dimensionality affects dynamics. We show that both the surface and the glass transition have a large impact on molecular dynamics, which in many aspects differs greatly from our expectations based on polymer glasses. For example, in the glassy phase the surface dynamics appear to be faster than in the bulk (i.e., liquid-like), yet just as heterogeneous (i.e., glass-like).
10.1088/1742-6596/2462/1/012053
Title
Near-surface dynamics of the ionic liquid EMIM-Ac above and below the glass transition
Author
D. Fujimoto, V. L. Karner, M. H. Dehn, S. R. Dunsiger, L. Hemmingsen, R. F. Kiefl, R. M. L. McFadden, C. A. Michal, G. D. Morris, R. Li, M. Pearson, D. Szunyogh, E. Thoeng, J. O. Ticknor, W. A. MacFarlane, M. Stachura
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012051
Year
2023
Abstract
In our prior work, we showed that β-detected nuclear magnetic resonance (β-NMR) was a good probe of bulk room temperature ionic liquid (RTIL) dynamics and dynamic heterogeneity. We now investigate how the surface modifies these properties, presenting the first depth-resolved β-NMR measurements in 1-ethyl-3-methylimidazolium acetate as a liquid, supercooled liquid, and glass. This interfacial region is important for understanding how constrained dimensionality affects dynamics. We show that both the surface and the glass transition have a large impact on molecular dynamics, which in many aspects differs greatly from our expectations based on polymer glasses. For example, in the glassy phase the surface dynamics appear to be faster than in the bulk (i.e., liquid-like), yet just as heterogeneous (i.e., glass-like).
10.1088/1742-6596/2462/1/012051
Title
Inverse Laplace transform approaches to βNMR relaxation
Author
W. A. MacFarlane, D. Fujimoto, R. M. L. McFadden
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012015
Year
2023
Abstract
Spin lattice relaxation is the simplest type of βNMR measurement. The usual approach is to implant a pulse of hyperpolarized nuclei and monitor the time-resolved β-decay asymmetry, yielding the ensemble average spin-lattice relaxation. In the simplest case, the asymmetry decays exponentially with a characteristic time constant T1, but this ideal is rarely obtained in practice. In most data, the relaxation is more complicated. This can be the result of multiple crystallographic sites for the implanted probe each having a distinct T1. The sample may also be inhomogeneous due to: impurities or defects (including interfaces that are particularly important for thin films), intrinsic phase separation, or, if it is a glass. There may also be a background signal from probe ions that stop outside the sample. The general approach to this problem has been the ad hoc development of an appropriate relaxation model that avoids overparametrization. Given the prevalence of more complicated relaxation, it is crucial to develop a systematic approach to relaxation modelling. The decomposition of a relaxing signal into exponentials is, however, a mathematically ill-posed problem. This feature is intrinsic and unavoidable, but there are a number of methods to accommodate it for noisy real-world data, including nuclear spin relaxation. Here we demonstrate one of the best and most commonly used methods, Tikhonov regularization for the inverse Laplace transform, implemented for the particular features of βNMR relaxation data, most importantly the strong time dependence of the statistical uncertainty stemming from the radioactive lifetime of the probe.
10.1088/1742-6596/2462/1/012015
Title
The site and high field βNMR properties of 8Li+ implanted in α-Al2O3
Author
W. A. MacFarlane, J. K. Shenton, Z. Salman, A. Chatzichristos, D. L. Cortie, M. Dehn, D. Fujimoto, V. L. Karner, R. F. Kiefl, D. Koumoulis, C. D. P. Levy, R. M. L. McFadden, I. McKenzie, G. D. Morris, M. R. Pearson, M. Stachura, J. O. Ticknor
Journal
Journal of Physics: Conference Series
Volume
2462
Pages
012009
Year
2023
Abstract
We present high (> 2 T) magnetic field βNMR measurements of 8Li+ implanted in single crystals of sapphire, a commonly used backing material for other samples. From the well-resolved quadrupolar splitting, we extract the electric field gradient (EFG) at the implanted 8Li+ site. Comparison with supercell density functional theory calculations of the EFG allows us to identify the octahedral interstitial site as the most likely candidate. In contrast to the zero field βNQR spectra, where multiple singals are detected, only a single site is evident at high field. We discuss possible explanations for this discrepancy. The spin lattice relaxation is extremely slow (1/T1 < 0.02 s−1) over a broad temperature range from 4 to 300 K, demonstrating that cross relaxation with the 27Al nuclear spins is quenched in such high magnetic fields.
10.1088/1742-6596/2462/1/012009
2022
Title
First βNMR results on SRF samples at TRIUMF
Author
E. Thoeng, R. M. L. McFadden, P. Kolb, T. Junginger, M. Asaduzzaman, R. E. Laxdal, V. L. Karner, D. Fujimoto, A. Chatzichristos, J. O. Ticknor, J. R. Adelman, M. H. Dehn, C. D. P. Levy, R. Li, I. McKenzie, M. Stachura, S. R. Dunsiger, G. D. Morris, W. A. MacFarlane, R. F. Kiefl, D. L. Cortie
Journal
Proceedings of the International Conference on RF Superconductivity
Volume
20
Pages
365-371
Year
2022
Abstract
The βNMR (β-detected nuclear magnetic resonance) facility at TRIUMF offers the possibility of depth-resolved probing of the Meissner state over the first 100 nm below a sample surface. The measurement can give the attenuation of the applied magnetic field, as a function of depth. The technique can be especially important when probing layered systems like the dirty/clean S-S (superconductor-superconductor) bi-layer and S-I-S (Superconductor-Insulator-Superconductor) structures. The TRIUMF SRF (Superconducting RF) group has recently completed first measurements at beta-NMR on Nb samples with various treatments. The results and method will be reported.
10.18429/JACoW-SRF2021-TUOFDV08
2019
Title
Progress of TRIUMF Beta-SRF facility for novel SRF materials
Author
E. Thoeng, R. A. Baartman, P. Kolb, R. E. Laxdal, B. Matheson, G. Morris, N. Muller, S. Saminathan, T. Junginger
Journal
Proceedings of the International Conference on RF Superconductivity
Volume
19
Pages
964-967
Year
2019
Abstract
SRF cavities made with bulk Nb have been the backbone of high-power modern linear accelerators. Demands for higher energy and more efficient linear accelerators, however, have strained the capabilities of bulk Nb close to its fundamental limit. Several routes have been proposed using thin film novel superconductors (e.g. Nb3Sn), SIS multilayer, and N-doping. Beta-NMR techniques are more suitable for the characterization of Meissner state in these materials, due to the capability of soft-landing radioactive ions on the nanometer scale of London penetration depth, as compared to micrometer probe of the muSR technique. Upgrade of the existing beta-NQR beamline, combined with the capability of high parallel magnetic field (200 mT) are the scope of the beta-SRF facility which has been fully funded. All hardware required for the upgrade has also been procured. The status of the commissioning, which is currently in phase I, is reported here, together with the future schedule of phase II with the fully installed beta-SRF beamline. Finally, the detail layout of the completed beamline and sample requirements will be included in this paper which might be of interest of future users.
10.18429/JACoW-SRF2019-THP047
Title
Spin polarized beam for battery materials research: µ±SR and β-NMR
Author
J. Sugiyama
Journal
Hyperfine Interactions
Volume
240
Pages
17
Year
2019
Abstract
Spin polarized particles exhibiting beta decay, such as, muon and 8Li are very useful for detecting internal magnetic fields in solids. Here, I review our attempts to use these spin polarized beams for battery materials research. Due to a unique lifetime and gyromagnetic ratio of muon, a positive muon spin rotation and relaxation (µ+SR) technique is very popular for studying microscopic internal magnetic fields in condensed matters caused by electron and nuclear magnetism. Particularly in 2009, it was found that Li+ ion diffusion in LixCoO2, which is the most common cathode material in a Li-ion battery, is detectable with µ+SR even under the presence of paramagnetic Co ions (Sugiyama et al., Phys. Rev. Lett. 103, 147601, 2009), while NMR is unable to do so due to the effect of localized magnetic moments on a spin-lattice relaxation rate. Such finding opened the door for µ+SR on energy materials research. Since then, many battery materials have been investigated with µ+SR in order to determine their intrinsic diffusion coefficient (D) of Li+ and Na+ ions. Furthermore, using such intrinsic D, the other important parameters are successfully derived, such as, the reactive surface area, diffusion pathway, and density of mobile ions. In 2018, we have initiated to measure internal magnetic fields in solids with a negative muon, i.e. a µ-SR technique, in J-PARC (Sugiyama et al., Phys. Rev. Lett. 121, 087202, 2018). This will provide a new insight for microscopic internal magnetic fields from lattice sites, while µ+SR does so from interstitial sites. On the contrary, a long lifetime of 8Li (1.21 s) makes a 8Li β-NMR technique suitable for detecting both concentration and diffusion of Li in solids. Particularly in TRIUMF, since the implantation energy of 8Li is tunable from almost 0 to about 28 keV, we can measure both spin-lattice relaxation rate and spin-spin relaxation rate as a function of depth up to about 200 nm, as well as µ+SR using a low energy muon beam in PSI. These will clarify whether the space charge layer of Li+ exists at the interface between electrode and electrolyte material.
10.1007/s10751-019-1560-4
2018
Title
Beta-SRF - A new facility to characterize SRF materials near fundamental limits
Author
E. Thoeng, R. A. Baartman, R. E. Laxdal, B. Matheson, G. Morris, N. Muller, S. Saminathan, A. Chen, T. Junginger
Journal
Proceedings of the International Particle Accelerator Conference
Volume
9
Pages
4961-4963
Year
2018
Abstract
Demands of CW high-power LINAC require SRF cavities operating at the frontier of high accelerating gradient and low RF power dissipation, i.e. high quality factor (Q0). This requirement poses a challenge for standard surface treatment recipes of SRF cavities. In a recent breakthrough, elliptical SRF cavities doped with Nitrogen have been shown to improve Q0 by a factor of 3, close to the fundamental SRF limit. The fundamental mechanisms at microscopic level and optimum doping recipe, however, have still not fully been understood. Materials other than Nb have also been proposed for SRF cavities to overcome the fundamental limit already reached with Nitrogen doping, e.g. Nb3Sn, MgB2, and Nb-SIS multilayer. At TRIUMF, a unique experimental facility is currently being developed to address these issues. This facility will be able to probe local surface magnetic field in the order of the London Penetration Depth (several tens of nm) via β decay detection of a low-energy radioactive ion-beam. This allows depth-resolution and layer-by-layer measurement of magnetic field shielding effectiveness of different SRF materials at high-parallel field (up to 200 mT). Design and current development of this facility will be presented here, as well as commissioning and future measurements strategies for new SRF materials.
10.18429/JACoW-IPAC2018-THPML122
Title
TRIUMF MuSR and βNMR research facilities
Author
S. R. Kreitzman, G. D. Morris
Journal
JPS Conference Proceedings
Volume
21
Pages
011056
Year
2018
Abstract
The TRIUMF Centre for Molecular and Materials Sciences (MMS) supports a MuSR user facility and a βNMR research program. An overview of this infrastructure, and its future prospects, are presented.
10.7566/JPSCP.21.011056
Title
BnmrOffice: a free software for β-NMR data analysis
Author
H. Saadaoui
Journal
JPS Conference Proceedings
Volume
21
Pages
011049
Year
2018
Abstract
A data-analysis framework with a graphical user interface (GUI) is developed to analyze β-NMR spectra in an automated and intuitive way. This program, named BnmrOffice is written in C++ and employs the QT libraries and tools for designing the GUI, and the CERN’s Minuit optimization routines for minimization. The program runs under multiple platforms, and is available for free under the terms of the GNU GPL standards. The GUI is structured in tabs to search, plot and analyze data, along other functionalities. The user can tweak the minimization options; and fit multiple data files (or runs) using single or global fitting routines with pre-defined or new models. Currently, BnmrOffice reads TRIUMF’s MUD data and ASCII files, and can be extended to other formats.
10.7566/JPSCP.21.011049
Title
Comparison of 8Li and 9Li spin relaxation in SrTiO3 and Pt: a means to distinguish magnetic and electric quadrupolar sources of relaxation
Author
A. Chatzichristos, R. M. L. McFadden, V. L. Karner, D. L. Cortie, C. D. P. Levy, W. A. MacFarlane, G. D. Morris, M. R. Pearson, Z. Salman, R. F. Kiefl
Journal
JPS Conference Proceedings
Volume
21
Pages
011048
Year
2018
Abstract
We demonstrate that the ratio of 1/T1 spin-lattice relaxation rates (SLR) of two different isotopes (here 8Li and 9Li) can be used in order to identify the predominant relaxation mechanism within the β-NMR technique. We studied with both isotopes a Pt foil and two samples of single crystal SrTiO3. In Pt, the ratio of the SLR rates was 6.82(29), which is close to but less than the theoretical limit of ~7.68 for pure magnetic relaxation. In SrTiO3, the weighted averaged SLR ratio of the two samples was 2.7(3), which is close but larger than the theoretical limit of ~2.14 expected for pure electric quadrupolar relaxation. This indicates that the primary source of relaxation in SrTiO3 is electric quadrupolar in origin and that magnetic effects have a much smaller importance in this material. The low effective asymmetry of 9Li was the dominant cause of uncertainty of the measurements in this study. We propose a system of tagging the beta-decays in coincidence with the alpha decays that take place in two of the three primary decay channels of 9Li as a way of increasing the effective asymmetry and enhance the signal of 9Li β-NMR.
10.7566/JPSCP.21.011048
Title
On the use of 31Mg for β-detected NMR studies of solids
Author
R. M. L. McFadden, A. Chatzichristos, M. H. Dehn, D. Fujimoto, H. Funakubo, A. Gottberg, T. Hitosugi, V. L. Karner, R. F. Kiefl, M. Kurokawa, J. Lassen, C. D. P. Levy, R. Li, G. D. Morris, M. R. Pearson, S. Shiraki, M. Stachura, J. Sugiyama, D. M. Szunyogh, W. A. MacFarlane
Journal
JPS Conference Proceedings
Volume
21
Pages
011047
Year
2018
Abstract
It has long been desirable to develop a spin-1/2 nucleus as a probe for β-detected NMR studies of solid materials. As a pure magnetic probe, it would greatly compliment our most extensively used nucleus 8Li (spin-2), which is sensitive to both dipolar and quadrupolar interactions. Following the recent successful polarization of spin-1/2 31Mg at TRIUMF, we report here on its use to study solids where host magnesium atoms occupy lattice sites with cubic symmetry - a situation most directly comparable to (stable) 25Mg NMR. We show preliminary results in: rocksalt MgO; spinel MgAl2O4; and antifluorite Mg2Si, which is an interesting semiconducting thermoelectric. Deviations from the results with conventional 25Mg NMR are attributed to the systematics associated with the β-NMR technique. The 31Mg decay chain is found to complicate the extraction of spin-lattice relaxation rates due to a time-dependent background signal introduced by its progeny. The prospect of further use of 31Mg as a β-NMR probe for the study of condensed matter is good.
10.7566/JPSCP.21.011047
Title
Beta-detected NMR of LSAT and YSZ
Author
V. L. Karner, R. M. L. Mcfadden, M. H. Dehn, D. Fujimoto, A. Chatzichristos, G. D. Morris, M. R. Pearson, C. D. P. Levy, A. Reisner, L. H. Tjeng, R. F. Kiefl, W. A. Macfarlane
Journal
JPS Conference Proceedings
Volume
21
Pages
011024
Year
2018
Abstract
Using 8Li β-NMR we studied two cation substituted solid solutions: yttria-stabilized zirconia (YSZ) and (La,Sr)(Al,Ta)O3 (LSAT). LSAT showed well defined but highly broadened quadrupolar satellites, with a similar pattern to that observed in SrTiO3. In contrast, the resonance in YSZ showed a single, broad peak indicative of a cubic 8Li implantation site. The 8Li spin-lattice relaxation at 6.55 T, for both solid solutions, is very slow; while at 150 G, the relaxation in LSAT becomes faster due to the 27Al nuclear moments similar to Al2O3. For YSZ the low field relaxation rate is also relatively fast possibly due to mobile O2- anions.
10.7566/JPSCP.21.011024
Title
Beta detected NMR of LaAlO3
Author
V. L. Karner, R. M. L. Mcfadden, A. Chatzichristos, G. D. Morris, M. R. Pearson, C. D. P. Levy, Z. Salman, D. L. Cortie, R. F. Kiefl, W. A. Macfarlane
Journal
JPS Conference Proceedings
Volume
21
Pages
011023
Year
2018
Abstract
Using 8Li β-NMR we studied the temperature dependence of the spin-lattice relaxation in LaAlO3 in high magnetic field. The relaxation in LAO is composed of two components: a fast-relaxing signal with a small amplitude, and a large amplitude, slow relaxing component. The data was fit using a highly-constrained model which assumes that the temperature dependence of the slow and fast component is the same at all temperatures. The 8Li relaxation suggests a T2 temperature dependence, indicating that the relaxation mechanism could be due to a coupling between the quadrupole moment of 8Li and the soft-mode, low energy phonons in LAO.
10.7566/JPSCP.21.011023
Title
Exploring the dynamics of glasses using beta detected NMR
Author
V. L. Karner, T. Liu, I. Mckenzie, A. Chatzichristos, D. L. Cortie, G. D. Morris, R. F. Kiefl, R. M. L. Mcfadden, Z. Fakhraai, M. Stachura, W. A. Macfarlane
Journal
JPS Conference Proceedings
Volume
21
Pages
011022
Year
2018
Abstract
We report 8Li spin lattice relaxation in two forms of the molecular glass TPD, one a normal glass and one prepared in an ultrastable configuration. The relaxation is remarkably fast, similar to 8Li relaxation in other organic materials and shows a stretched exponential behavior typical of glasses with a small stretching exponent β = 0.3. At low temperature, there is little or no difference between the two glasses, while above 250 K, the relaxation in the denser ultrastable form is faster. In addition, in this temperature range, the data shows a significant thermal hysteresis.
10.7566/JPSCP.21.011022
Title
Challenge for detecting the interface between electrode and electrolyte with β-NMR
Author
J. Sugiyama, I. Umegaki, S. Shiraki, T. Hitosugi, R. M. L. McFadden, D. Wang, V. Karner, G. D. Morris, W. A. MacFarlane, R. F. Kiefl
Journal
JPS Conference Proceedings
Volume
21
Pages
011021
Year
2018
Abstract
It is widely believed that a space-charge layer (SCL) exists at the vicinity of a boundary between a solid electrolyte layer and electrode layer in an all solid-state Li-ion battery due to the difference of their chemical potentials, although there are no direct experimental evidences. Here, the Li concentration is predicted to decrease drastically in the SCL. In order to clarify whether SCL exists or not, we have attempted to measure the 8Li β-NMR spectrum for a multilayer sample, MgO (50  nm)/Li3PO4 (70  nm)/LiCoO2 (200  nm) as a function of implanted energy of 8Li. The resonance spectrum was fitted by a combination of two Lorentzians and one background signal. Furthermore, the line width of the resonance signal from the Li3PO4 layer is found to become broad towards the boundary with the LiCoO2 layer. This is consistent with the presence of an SCL.
10.7566/JPSCP.21.011021
Title
The spin relaxation of 8Li+ in gold at low magnetic field
Author
W. A. MacFarlane, K. H. Chow, M. D. Hossain, V. L. Karner, R. F. Kiefl, R. M. L. McFadden, G. D. Morris, H. Saadaoui, Z. Salman
Journal
JPS Conference Proceedings
Volume
21
Pages
011020
Year
2018
Abstract
Here we report the temperature and applied magnetic field dependence of the spin lattice relaxation of implanted into Au foil in the range 4 to 290 K and 3 to 150 G. Below about 50 G, relaxation due to the dynamic host lattice nuclear spins is important, becoming dominant below 20 G. At 150 G, this process is quenched, and the relaxation is Korringa-like. We report the first measurement of its temperature dependence which shows the characteristic features of the site change around 190 K. At lower field the relaxation is two component above 100 K and exhibits a strong peak at the site change, which we attribute to quadrupolar relaxation of the adjacent Au spins. We discuss the ingredients required for a quantitative theory of the low field relaxation.
10.7566/JPSCP.21.011020
Title
Developments in μSR and β NMR: beyond a muon lifetime
Author
R. F. Kiefl
Journal
JPS Conference Proceedings
Volume
21
Pages
011001
Year
2018
Abstract
Advances in the use of μSR and β-NMR are driven by technical developments. New methods were developed which allowed us to learn surprising things about muonium in semiconductors, its electronic structure, its relationship to hydrogen, its ability to diffuse via quantum tunneling, and its metastability. Similarly in the area of high Tc superconductors new capabilities in spectrometer design led to new information on the properties of superconducting vortices and how they interact. The development of low energy β-NMR at TRIUMF and LE-μSR at PSI has made it possible to study electronic and magnetic properties of thin films and interfaces where conventional NMR lacks the required sensitivity. Low energy β-NMR is almost identical to μSR in principle, but the longer lifetime of 8Li allows one to probe the system on a very different time scale. In this sense β-NMR can be viewed as a complement or extension of μSR.
10.7566/JPSCP.21.011001
2017
Title
Towards 31Mg-β-NMR resonance linewidths adequate for applications in magnesium chemistry
Author
M. Stachura, R. M. L. McFadden, A. Chatzichristos, M. H. Dehn, A. Gottberg, L. Hemmingsen, A. Jancso, V. L. Karner, R. F. Kiefl, F. H. Larsen, J. Lassen, C. D. P. Levy, R. Li, W. A. MacFarlane, G. D. Morris, S. Pallada, M. R. Pearson, D. Szunyogh, P. W. Thulstrup, A. Voss
Journal
Hyperfine Interactions
Volume
238
Pages
32
Year
2017
Abstract
The span of most chemical shifts recorded in conventional 25Mg-NMR spectroscopy is ~100 ppm. Accordingly, linewidths of ~10 ppm or better are desirable to achieve adequate resolution for applications in chemistry. Here we present first high-field 31Mg-β-NMR measurements of 31Mg+ ions implanted into a MgO single crystal carried out at the ISAC facility at TRIUMF. The resonances recorded at 2.5 T and 3.5 T show strong linewidth dependency on the applied RF power, ranging from ~419 ppm for the highest RF power down to ~48 ppm for the lowest one.
10.1007/s10751-017-1408-8
2016
Title
Development of a polarized 31Mg+ beam as a spin-1/2 probe for BNMR
Author
C. D. P. Levy, M. R. Pearson, M. H. Dehn, V. L. Karner, R. F. Kiefl, J. Lassen, R. Li, W. A. MacFarlane, R. M. L. McFadden, G. D. Morris, M. Stachura, A. Teigelhöfer, A. Voss
Journal
Hyperfine Interactions
Volume
237
Pages
162
Year
2016
Abstract
A 28 keV beam of 31Mg+ ions was extracted from a uranium carbide, proton-beam-irradiated target coupled to a laser ion source. The ion beam was nuclear-spin polarized by collinear optical pumping on the 2S1/2-2P1/2 transition at 280 nm. The polarization was preserved by an extended 1 mT guide field as the beam was transported via electrostatic bends into a 2.5 T longitudinal magnetic field. There the beam was implanted into a single crystal MgO target and the beta decay asymmetry was measured. Both hyperfine ground states were optically pumped with a single frequency light source, using segmentation of the beam energy, which boosted the polarization by approximately 50 % compared to pumping a single ground state. The total decay asymmetry of 0.06 and beam intensity were sufficient to provide a useful spin-1/2 beam for future BNMR experiments. A variant of the method was used previously to optically pump the full Doppler-broadened absorption profile of a beam of 11Be+ with a single-frequency light source.
10.1007/s10751-016-1372-8
2014
Title
The initial state of optically polarized 8Li+ from the β-NMR in bismuth
Author
W. A. MacFarlane, C. D. P. Levy, M. R. Pearson, T. Buck, K. H. Chow, A. N. Hariwal, R. F. Kiefl, F. H. McGee, G. D. Morris, D. Wang
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012059
Year
2014
Abstract
Unlike the positive muon, β-NMR probe nuclei must be actively polarized. At the TRIUMF ISAC facility this is accomplished by in-flight collinear optical pumping with resonant circularly polarized laser light. This reliably produces a high degree of polarization, but the detailed state populations in the beam emerging from the optical polarizer are not well known. These populations are significant as they represent the initial state of the ensemble of probe spins implanted in a β-NMR experiment. Here we use the well-resolved quadrupolar split spectrum of 8Li+ in a high purity single crystal of bismuth to extract the sublevel populations under typical polarizer operating conditions, accounting for the spin relaxation in this semimetal.
10.1088/1742-6596/551/1/012059
Title
A brief survey of β-detected NMR of implanted 8Li+ in organic polymers
Author
F. H. McGee, I. McKenzie, T. Buck, C. R. Daley, J. A. Forrest, M. Harada, R. F. Kiefl, C. D. P. Levy, G. D. Morris, M. R. Pearson, J. Sugiyama, D. Wang, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012039
Year
2014
Abstract
Unlike the positive muon, we expect the chemistry of the implanted 8Li+ β-NMR probe in organic polymers to be simply that of the monovalent ion, but almost nothing is known about the NMR of isolated Li+ in this context. Here, we present a brief survey of 8Li+ β-NMR in a variety of insulating polymers at high magnetic field, including polyimide, PET, polycarbonate, polystyrene and polyethylene oxide. In all cases, we find a large-amplitude, broad Lorentzian resonance near the Larmor frequency, consistent with the expected diamagnetic charge state. We also find remarkably fast spin-lattice relaxation rates 1/T1. There is very little dependence of either linewidth or 1/T1 on the proton density, the main source of nuclear dipolar magnetic fields, leading us to conclude the main contribution to both broadening and spin relaxation at room temperature is quadrupolar in origin. This behaviour is very different from crystalline insulators such as MgO and Al2O3, and suggests that 8Li+ β-NMR will be an important probe of polymer dynamics. Additionally, we note dramatically different behaviour of one sample above its glass transition, motivating the construction of a high temperature spectrometer to enable further exploration at elevated temperature.
10.1088/1742-6596/551/1/012039
Title
β-detected nuclear quadrupole resonance and relaxation of 8Li+ in sapphire
Author
Z. Salman, K. H. Chow, M. D. Hossain, R. F. Kiefl, C. D. P. Levy, T. J. Parolin, M. R. Pearson, H. Saadaoui, D. Wang, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012034
Year
2014
Abstract
We report detailed behaviour of low energy 8Li implanted near the surface of α-Al2O3 single crystal, as revealed by beta-detected NQR of 8Li. We find that the implanted 8Li occupies at least two sites with non-cubic symmetry in the Al2O3 lattice. In both sites the 8Li experiences axially symmetric electric field gradient, with the main principal axis along the c-crystallographic direction. The temperature and field dependence of the spin lattice relaxation of 8Li in α-Al2O3, indicate that the 8Li diffusion is negligible on the scale of its lifetime, 1.21 s.
10.1088/1742-6596/551/1/012034
Title
8Li+ β-NMR in the cubic insulator MgO
Author
W. A. MacFarlane, T. J. Parolin, D. L. Cortie, K. H. Chow, M. D. Hossain, R. F. Kiefl, C. D. P. Levy, R. M. L. McFadden, G. D. Morris, M. R. Pearson, H. Saadaoui, Z. Salman, Q. Song, D. Wang
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012033
Year
2014
Abstract
We present extensive high magnetic field β-NMR measurements of 8Li+ implanted in single crystals of MgO. The narrow resonance, consistent with a cubic 8Li+ site, likely the tetrahedral interstitital, is used routinely as a reference for shift measurements. We show the intrinsic linewidth is on the order of 200 Hz, allowing a frequency determination to an accuracy of a few Hz. We find no implantation energy dependence of the resonance within a few ppm, but there is evidence of slow spin dynamics in hole-burning measurements. The spin lattice relaxation is slow. The temperature dependence reveals interesting changes at low temperature whose origin remains uncertain.
10.1088/1742-6596/551/1/012033
Title
β-NMR of 8Li+ in rutile TiO2
Author
R. M. L. McFadden, D. L. Cortie, D. J. Arseneau, T. J. Buck, C.-C. Chen, M. H. Dehn, S. R. Dunsiger, R. F. Kiefl, C. D. P. Levy, C. Li, G. D. Morris, M. R. Pearson, D. Samuelis, J. Xiao, J. Maier, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012032
Year
2014
Abstract
We report preliminary low-energy β-NMR measurements of 8Li+ implanted in single crystal rutile TiO2 at an applied field of 6.55 T and 300 K. We observe a broad 12 kHz wide quadrupole split resonance with unresolved features and a sharp component at the Larmor frequency. The line broadening may be caused by overlapping multi-quantum transitions or motion of 8Li+ on the scale of its lifetime (1.21 s). We also find spin-lattice relaxation that is relatively fast compared to other wide band gap insulators. The origin of this fast relaxation is also likely quadrupolar and may be due to anisotropic 8Li+ diffusion.
10.1088/1742-6596/551/1/012032
Title
β-NMR study of a buried Mn δ-doped layer in a silicon host
Author
D. Cortie, T. Buck, R. M. L. McFadden, J. Xiao, C. D. P. Levy, M. Dehn, M. Pearson, G. D. Morris, S. R. Dunsiger, R. F. Kiefl, F. J. Rueß, A. Fuhrer, W. A. MacFarlane
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012023
Year
2014
Abstract
Low temperature growth methods were used to encapsulate a buried Mn δ-doping layer into a silicon host. A β-NMR investigation was performed of the magnetic properties in the temperature range 10-300 K using spin-polarized 8Li+. A depth-dependent broadening and shift of the NMR resonance was detected that is consistent with internal fields distributed at depths of 10-30 nm beneath the surface. At low temperatures, a negative relative shift occurred and the resonance was significantly broadened. At 300 K the line-shape could be described by a single Gaussian line, however, at 10 K the line is best approximated by a two component Lorentzian shape consisting of a broad and narrow component as anticipated for a diluted magnetic alloy. The overall magnitude of the resonance shift at both temperatures is small suggesting a weak interaction between the 8Li+ and the magnetic Mn environment.
10.1088/1742-6596/551/1/012023
Title
8Li β-NMR study of epitaxial LixCoO2 films
Author
J. Sugiyama, M. Harada, H. Oki, S. Shiraki, T. Hitosugi, O. Ofer, Z. Salman, Q. Song, D. Wang, H. Saadaoui, G. D. Morris, K. H. Chow, W. A. MacFarlane, R. F. Kiefl
Journal
Journal of Physics: Conference Series
Volume
551
Pages
012009
Year
2014
Abstract
n order to investigate the diffusive motion of Li+ in a thin film electrode material for Li-ion batteries, we have measured β-NMR spectra of 8Li+ ions implanted into epitaxial films of Li0.7CoO2 and LiCoO2 in the temperature range between 10 and 310 K. Below 100 K, the spin-lattice relaxation rate (1/T1) in the Li0.7CoO2 film increased with decreasing temperature, indicating the appearance and evolution of localized magnetic moments, as observed with μ+SR. As temperature is increased from 100 K, 1/T1 starts to increase above ~200 K, where both Li-NMR and μ+SR also sensed an increase in 1/T1 due to Li-diffusion. Interestingly, such diffusive behavior was found to depend on the implantation energy, possibly because the surface of the film is decomposed due to chemical instability of the Li0.7CoO2 phase in air. Such diffusive behavior was not observed for the LiCoO2 film up to 310 K.
10.1088/1742-6596/551/1/012009
2012
Title
Use of the strong collision model to calculate spin relaxation
Author
D. Wang, K. H. Chow, M. Smadella, M. D. Hossain, W. A. MacFarlane, G. D. Morris, O. Ofer, E. Morenzoni, Z. Salman, H. Saadaoui, Q. Song, R. F. Kiefl
Journal
Physics Procedia
Volume
30
Pages
38-41
Year
2012
Abstract
The strong collision model is used to calculate spin relaxation of a muon or polarized radioactive nucleus in contact with a fluctuating environment. We show that on a time scale much longer than the mean time between collisions (fluctuations) the longitudinal polarization decays exponentially with a relaxation rate equal to a sum of Lorentzians - one for each frequency component in the static polarization function ps(t).
10.1016/j.phpro.2012.04.035
Title
8Li+ Knight shift and resonance in the enhanced paramagnet platinum studied by βNMR
Author
O. Ofer, K. H. Chow, I. Fan, M. Egilmez, T. J. Parolin, M. D. Hossain, J. Jung, Z. Salman, R. F. Kiefl, C. D. P. Levy, G. D. Morris, M. R. Pearson, H. Saadaoui, Q. Song, D. Wang, W. A. MacFarlane
Journal
Physics Procedia
Volume
30
Pages
156-159
Year
2012
Abstract
We report the behavior of 8Li+ implanted into Platinum foil as revealed by β-detected Nuclear Magnetic Resonance (β-NMR). At an applied field of 4.1 T, a single resonance is observed, which is attributed to Li in an octahedral interstitial site. The temperature dependence of the Knight shift for this resonance is monitored at temperatures ranging from 4 to 300 K. Over this range the Knight shift is found to be linearily dependent on the temperature.
10.1016/j.phpro.2012.04.062
Title
β-detected NMR study of semi-insulating GaAs
Author
Q. Song, K. H. Chow, M. D. Hossain, R. F. Kiefl, G. D. Morris, C. D. P. Levy, H. Saadaoui, M. Smadella, D. Wang, B. Kardasz, B. Heinrich, W. A. MacFarlane
Journal
Physics Procedia
Volume
30
Pages
227-230
Year
2012
Abstract
A beta-detected NMR experiment is carried out on a semi-insulating GaAs crystal using a low energy spin polarized 8Li+ beam to investigate the magnetic properties as a function of temperature and depth. The range of depths probed, from ~137 nm down to ~17 nm, coincides with the region of electronic band-bending due to the surface. We find a resonance broadened by the host nuclear dipoles, consistent with an earlier report [6], but using a pulsed radio frequency scheme, we are able to make higher resolution measurements. We find a small negative shift of the resonance (relative to an MgO reference) at room temperature that is independent of depth. Remarkably, as the temperature is reduced below about 150 K, the resonance shifts negatively and becomes depth dependent, with a larger negative shift deeper into the sample. This shift saturates below 10 K, i.e. it does not follow a Curie's law that might be expected for dilute magnetic impurities. Possible origins are discussed.
10.1016/j.phpro.2012.04.079
Title
β-Detected NMR search for magnetic phase separation in epitaxial GaAs:Mn
Author
Q. Song, K. H. Chow, R. I. Miller, I. Fan, M. D. Hossain, R. F. Kiefl, G. D. Morris, S. R. Kreitzman, C. D. P. Levy, T. J. Parolin, M. R. Pearson, Z. Salman, H. Saadaoui, M. Smadella, D. Wang, K. M. Yu, X. Liu, J. K. Furdyna, W. A. MacFarlane
Journal
Physics Procedia
Volume
30
Pages
174-177
Year
2012
Abstract
To test for the microscopic magnetic phase separation in the dilute magnetic semiconductor Ga1-xMnxAs suggested by low energy muon spin rotation measurements [1], we present a detailed analysis of the amplitudes of the 8Li β-detected nuclear magnetic resonance in an epitaxially grown thin film of x = 5.4 % Mn doped GaAs on a semi-insulating GaAs substrate with magnetic transition temperature TC = 72 K. The spectrum at 100 K corresponds to 73 % of the full room temperature amplitude, and at 60 K to about 62 %. The 11 % loss of signal through the magnetic transition is much smaller than that ~50 % found by low energy μSR [1], and may be entirely due to an amplitude change intrinsic to GaAs. This lack of evidence for phase separation is, however, consistent with the full volume fraction magnetism found by a second low energy μSR measurement on a different sample using weak transverse field [2].
10.1016/j.phpro.2012.04.066
Title
Proximal magnetometry of monolayers of magnetic moments
Author
Z. Salman, S. J. Blundell
Journal
Physics Procedia
Volume
30
Pages
168-173
Year
2012
Abstract
We present a method to measure the magnetic properties of monolayers and ultra-thin films of magnetic material. The method is based on low energy muon spin rotation and β-detected nuclear magnetic resonance measurements. A spin probe is used as a "proximal" magnetometer by implanting it in the substrate, just below the magnetic material. We calculate the expected magnetic field distribution sensed by the probe and discuss its temperature and implantation depth dependencies. This method is highly suitable for measuring the magnetic properties of monolayers of single molecule magnets, but can also be extended to ultra-thin magnetic films.
10.1016/j.phpro.2012.04.065
Title
Observing cross-relaxation with depth-resolved 8Li β-NMR
Author
K. H. Chow, A. I. Mansour, I. Fan, G. D. Morris, Z. Salman, T. Dunlop, W. A. MacFarlane, R. F. Kiefl, H. Saadaoui, O. Mosendz, B. Kardasz, B. Heinrich, J. Jung, C. D. P. Levy, M. R. Pearson, T. J. Parolin, D. Wang, M. D. Hossain, Q. Song, M. Smadella
Journal
Physics Procedia
Volume
30
Pages
16-19
Year
2012
Abstract
In the paper, we review some of the progress that has been made, at the ISAC β-NMR facility, towards observing 8Li+ high field cross-relaxation phenomena in copper. The clearest observation of these phenomena is via the appearance of peaks in the field dependence of the relaxation rates of the 8Li+ polarization.
10.1016/j.phpro.2012.04.030
2011
Title
The development of pure β-NQR techniques for measurements of nuclear ground state quadrupole moments in lithium isotopes
Author
A. Voss, M. R. Pearson, J. Billowes, F. Buchinger, K. H. Chow, J. E. Crawford, M. D. Hossein, R. F. Kiefl, C. D. P. Levy, W. A. MacFarlane, E. Mané, G. D. Morris, T. J. Parolin, H. Saadaoui, Z. Salman, M. Smadella, Q. Song, D. Wang
Journal
Journal of Physics: Conference Series
Volume
312
Pages
092063
Year
2011
Abstract
A β-NQR spectrometer becomes a powerful tool to study changes in nuclear ground state properties along isotopic chains when coupled to a laser excitation beamline to polarise the nuclei of interest. Recently, the β-NQR technique in a zero magnetic field has been applied for the first-time to measure ratios of static nuclear quadrupole moments of 8,9,11Li. Preliminary results of the experiment determining the ratios Q9/Q8 and Q11/Q9 show agreement with present literature values with improved precision.
10.1088/1742-6596/312/9/092063
2010
Title
Development of the collinear laser beam line at TRIUMF
Author
C. D. P. Levy, M. R. Pearson, G. D. Morris, K. H. Chow, M. D. Hossain, R. F. Kiefl, R. Labbé, J. Lassen, W. A. MacFarlane, T. J. Parolin, H. Saadaoui, M. Smadella, Q. Song, D. Wang
Journal
Hyperfine Interactions
Volume
196
Pages
287-294
Year
2010
Abstract
The low-energy collinear laser beam line at ISAC routinely produces highly nuclear-spin polarized beams of 8Li+ for depth-controlled studies of thin films and near-surface phenomena. It also is used for nuclear structure and fundamental symmetry studies requiring other beams of polarized lithium and sodium isotopes. Further development of polarized 20F and 11Be beams is described, the latter in some detail. Laser fluorescence spectroscopy at high sensitivity using unpolarized bunched beams is briefly mentioned.
10.1007/s10751-009-0148-9
2009
Title
Surface dependent structural phase transition in SrTiO3 observed with spin relaxation of 8Li
Author
M. Smadella, Z. Salman, K. H. Chow, M. Egilmez, I. Fan, M. D. Hossain, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, W. A. MacFarlane, A. I. Mansour, G. D. Morris, T. J. Parolin, M. Pearson, H. Saadaoui, Q. Song, D. Wang
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
924-926
Year
2009
Abstract
We investigate the 105 K structural phase transition in SrTiO3 using depth controlled measurements of the spin relaxation of 8Li. The measurements were performed in zero external magnetic field and rely on the local electric field gradient (EFG) at the crystalline implantation site of the 8Li (I = 2) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the EFG in some 8Li implantation sites, resulting in an observable loss of 8Li polarization. This loss of polarization begins at a temperature T*, indicating there is some loss of cubic symmetry well above the bulk transition. We find that the value of is unaffected by the range of implantation depths available (10-150 nm); however, the temperature dependence of the polarization depends on the surface preparation of the SrTiO3 sample.
10.1016/j.physb.2008.11.135
Title
Nuclear spin relaxation/resonance of 8Li in Al
Author
D. Wang, Z. Salman, K. H. Chow, I. Fan, M. D. Hossain, T. A. Keeler, R. F. Kiefl, C. D. P. Levy, A. I. Mansour, G. D. Morris, M. R. Pearson, T. J. Parolin, H. Saadaoui, M. Smadella, Q. Song, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
920-923
Year
2009
Abstract
A low energy beam of spin polarized 8Li has been used to study the behaviour of isolated 8Li implanted into a 150 nm thick film of Al on an MgO substrate. The spin relaxation rate 1/T1 and β-NMR lineshape were measured as a function of temperature in a large magnetic field of 4.1 T. The resonances from different sites are unresolved due to the large nuclear dipolar interaction with the host 27Al magnetic dipole moments. Nevertheless the temperature variation of the site averaged and Knight shift show evidence for a transition between the octahedral O and substitutional S sites at about 150 K, as observed in other fcc metals.
10.1016/j.physb.2008.11.136
Title
Hyperfine fields in thin Pd films by beta-detected NMR
Author
T. J. Parolin, Z. Salman, J. Chakhalian, Q. Song, K. H. Chow, G. D. Morris, M. Egilmez, I. Fan, M. D. Hossain, T. A. Keeler, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, A. I. Mansour, R. I. Miller, M. R. Pearson, H. Saadaoui, M. Smadella, D. Wang, M. Xu, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
917-919
Year
2009
Abstract
Using low energy beta-detected nuclear magnetic resonance (β-NMR), the Knight shift and spin-lattice relaxation rate of dilute 8Li+ implanted into a 28 nm Pd film on a MgO substrate were studied as a function of temperature. The shift of the resonance is negative, but much smaller in magnitude than observed in two other much thicker samples. The corresponding spin-lattice relaxation rates are found to be linear with temperature T, but are roughly 50 % slower than the rates measured in a Pd foil. Potential explanations are discussed.
10.1016/j.physb.2008.11.137
Title
The spin lattice relaxation of 8Li in simple metals
Author
M. D. Hossain, H. Saadaoui, T. J. Parolin, Q. Song, D. Wang, M. Smadella, K. H. Chow, M. Egilmez, I. Fan, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, G. D. Morris, M. R. Pearson, Z. Salman, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
914-916
Year
2009
Abstract
We report the modification to the linear temperature dependence of the Korringa nuclear spin-lattice relaxation rate of an implanted NMR probe in silver, as it makes a thermally activated site change. We develop a simple model of this phenomenon, which is found in a number of metals including Au and Nb.
10.1016/j.physb.2008.11.157
Title
Cross-relaxation of 8Li+ in copper
Author
A. I. Mansour, G. D. Morris, Z. Salman, K. H. Chow, T. Dunlop, J. Jung, I. Fan, W. A. MacFarlane, R. F. Kiefl, T. J. Parolin, H. Saadaoui, D. Wang, M. D. Hossain, Q. Song, M. Smadella, O. Mosendz, B. Kardasz, B. Heinrich, C. D. P. Levy, M. R. Pearson
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
910-913
Year
2009
Abstract
The "cross-relaxation" method (also called "level-crossing resonance" or "avoided level-crossing") is a powerful technique that can be used to provide detailed structural and site information on impurities in materials. In this paper, we report on the development of the cross-relaxation technique for at the β-detected nuclear magnetic resonance (β-NMR) facility located in TRIUMF in Vancouver. The measurements were carried out on a <110> Cu single crystal where the relaxation rate of the polarization was monitored as a function of the applied longitudinal magnetic field. The occurrence of cross-relaxation, at a particular magnetic field, between the and the surrounding nuclei is evident as a resonant enhancement of the relaxation rate at the level crossing field. We discuss inferences about the site and structure of 8Li+ in Cu from this data.
10.1016/j.physb.2008.11.138
Title
β-NMR of a thin Pt film
Author
I. Fan, K. Chow, T. Parolin, M. Egilmez, M. Hossain, J. Jung, T. Keeler, R. Kiefl, S. Kreitzman, C. Levy, R. Ma, G. Morris, M. Pearson, H. Saadaoui, Z. Salman, M. Smadella, Q. Song, D. Wang, M. Xu, W. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
906-909
Year
2009
Abstract
We report beta-detected NMR (β-NMR) measurements on a 50 nm thick platinum (Pt) film grown on a magnesium oxide (MgO) substrate. The frequency of the β-NMR resonance in Pt was compared to the MgO reference frequency to estimate the Knight shift at various temperatures (100-300 K). The Knight shift was found to be negative and strongly temperature dependent. The implications are discussed and compared to other transition metals that have been studied via β-NMR previously.
10.1016/j.physb.2008.11.139
Title
Beta-detected NMR study of the local magnetic field in epitaxial GaAs:Mn
Author
Q. Song, K. Chow, R. Miller, I. Fan, M. Hossain, R. Kiefl, S. Kreitzman, C. Levy, T. Parolin, M. Pearson, Z. Salman, H. Saadaoui, M. Smadella, D. Wang, K. Yu, X. Liu, J. Furdyna, W. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
892
Year
2009
Abstract
A low energy beam of spin polarized 8Li+ has been employed to study the magnetic field distribution in an epitaxial thin film of 5.4 % Mn doped GaAs(180 nm) on a (100) GaAs substrate via beta-detected NMR. The spectrum is a strong function of the implantation energy in the range 28-3 keV. In the magnetic layer, there is no indication of a missing fraction, and even more remarkable, there is a broad negatively shifted resonance. The spin lattice relaxation rate is, however, much faster in the Mn doped layer than in the substrate. A sharp peak characteristic of nonmagnetic GaAs is observed down to the lowest implantation energy, for which none of the Li should reach the substrate. This unexpected depth dependence is discussed.
10.1016/j.physb.2008.11.143
Title
Vortex lattice disorder in YBa2Cu3O7-δ studied with β-NMR
Author
H. Saadaoui, W. A. MacFarlane, G. D. Morris, Z. Salman, K. H. Chow, I. Fan, M. D. Hossain, R. Liang, A. I. Mansour, T. J. Parolin, M. Smadella, Q. Song, D. Wang, R. F. Kiefl
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
730
Year
2009
Abstract
In this paper, we report β-NMR measurements in thin Ag films deposited on the surface of YBa2Cu3O7-δ (YBCO) in the vortex state. The resonance in the Ag overlayer broadens dramatically below the superconducting transition temperature Tc, as expected from the underlying vortex lattice in the YBCO. However, the lineshape is much broader and more symmetric than expected for an ideal vortex lattice. These results indicate the observed field distribution in the Ag overlayer is dominated by extrinsic, long length scale disorder.
10.1016/j.physb.2008.11.229
Title
β-NMR investigation of the vortex lattice near the interface of silver and Pr1.85Ce0.15CuO4-δ thin films
Author
H. Saadaoui, W. A. MacFarlane, Z. Salman, G. D. Morris, K. H. Chow, I. Fan, P. Fournier, M. D. Hossain, T. A. Keeler, S. R. Kreitzman, C. D. P. Levy, A. I. Mansour, R. I. Miller, T. J. Parolin, M. R. Pearson, Q. Song, D. Wang, R. F. Kiefl
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
727-729
Year
2009
Abstract
In this paper, we report observation of the vortex lattice above the surface of high-temperature superconductors Pr1.85Ce0.15CuO4-δ using beta-detected NMR (β-NMR) of implanted in a 40 nm thick Ag overlayer. The resonance in Ag broadens dramatically below the transition temperature Tc as expected from the vortex lattice in the underlying superconductor. However, the lineshape is nearly symmetric with the absence of a high-field tail and exhibits a slight positive shift of the average field below Tc.
10.1016/j.physb.2008.11.187
Title
Search for time-reversal symmetry breaking order at the (110) interface of YBa2Cu3O7-δ using βNMR
Author
H. Saadaoui, G. D. Morris, K. H. Chow, M. D. Hossain, C. D. P. Levy, T. J. Parolin, M. R. Pearson, Z. Salman, M. Smadella, Q. Song, D. Wang, P. J. Hentges, L. H. Greene, R. F. Kiefl, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
724-726
Year
2009
Abstract
In this paper, we report initial βNMR measurements seeking the spontaneous magnetic fields associated with a time-reversal symmetry breaking (TRSB) order at the (110) interface of the high temperature superconductor YBa2Cu3O7-δ (YBCO). A 2 keV beam of highly spin-polarized 8Li+ was implanted into a thin overlayer of silver sputtered onto an oriented YBCO film. The NMR of 8Li in the Ag layer showed additional broadening with an onset below the superconducting transition temperature Tc. This is evidence of spontaneous disordered magnetism which could be associated with TRSB order.
10.1016/j.physb.2008.11.188
Title
Spin lattice relaxation of 8Li in a ferromagnetic EuO epitaxial thin film
Author
Q. Song, K. H. Chow, M. Egilmez, I. Fan, M. D. Hossain, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, G. D. Morris, T. J. Parolin, M. R. Pearson, Z. Salman, H. Saadaoui, M. Smadella, D. Wang, N. J. C. Ingle, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
619-621
Year
2009
Abstract
We inject a low energy spin polarized 8Li+ beam into an epitaxially grown multilayer film consisting of Au(20 nm)/EuO(100 nm)/LaAlO3, and investigate the nuclear spin relaxation at 3.33 T. The relaxation varies with implantation energy below 28 keV as the fraction of the probe 8Li stopping in each layer changes. We attribute the fast relaxating component to the EuO, while the much slower relaxation has contributions from both the Au and the substrate. However, fast relaxation is still observed at the lowest implantation energy where all the 8Li stops in the Au capping layer. This may be due to a proximity effect from the EuO.
10.1016/j.physb.2008.11.110
Title
Polarisation of a spin-1/2 β-NMR probe 11Be using collinear laser optical pumping
Author
C. D. P. Levy, M. R. Pearson, G. D. Morris, J. Lassen, K. H. Chow, M. D. Hossain, R. F. Kiefl, R. Labbé, W. A. MacFarlane, T. J. Parolin, L. Root, H. Saadaoui, M. Smadella, D. Wang
Journal
Physica B: Condensed Matter
Volume
404
Issue
5-7
Pages
1010-1012
Year
2009
Abstract
Spin 1/2 probes have special importance in the field of NMR, since they have no electric quadrupole moment and are thus pure magnetic sensors. The absence of quadrupolar splittings greatly simplifies the NMR frequency spectrum. That the muon is spin 1/2 is one of the reasons it has become so useful as a magnetic probe. Until now there has been no spin 1/2 probe suitable for beta-detected NMR. Such a probe would be particularly useful in complex materials, which are in general non-cubic. In this paper we describe the development of a low energy beam of spin-polarised 11Be, which is the lightest spin 1/2 isotope suitable for β-NMR. The intensity of the 11Be+ beam - generated by a laser ionisation source - is about 106/s. The 11Be nuclei are polarised by collinear laser optical pumping with an externally frequency doubled dye laser tuned to the 2S1/2-2P1/2 transition of 11Be+ at 313 nm.
10.1016/j.physb.2008.11.205
2007
Title
Development of the 8Li cross-relaxation technique: applications in semiconductors and other condensed matter systems
Author
A. I. Mansour, G. D. Morris, Z. Salman, K. H. Chow, T. Dunlop, J. Jung, I. Fan, W. A. MacFarlane, R. F. Kiefl, T. J. Parolin, H. Saadaoui, D. Wang, M. D. Hossain, Q. Song, M. Smadella, O. Mosendz, B. Kardasz, B. Heinrich
Journal
Physica B: Condensed Matter
Volume
401-402
Pages
662-665
Year
2007
Abstract
The so-called "cross-relaxation" method is a powerful technique that can be used to provide detailed structural and site information on impurities in condensed matter systems, including semiconductors. In this paper, we report on the progress of its development at the new 8Li β-detected nuclear magnetic resonance (β-NMR) facility located in TRIUMF in Vancouver, Canada. We present first measurements using this method on a Cu single crystal and discuss future application for studies of isolated impurities in semiconductors.
10.1016/j.physb.2007.09.046
Title
8Li in GaAs studied with β-NMR
Author
T. Dunlop, A. I. Mansour, Z. Salman, K. H. Chow, I. Fan, J. Jung, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, W. A. MacFarlane, G. Morris, T. J. Parolin
Journal
Physica B: Condensed Matter
Volume
401-402
Pages
254-257
Year
2007
Abstract
β-NMR has been used to study isolated spin polarized 8Li+ in bulk crystalline GaAs. At low temperatures a large fraction (at least 70 %) of the Li end up in locations with cubic symmetry (e.g. a tetrahedral interstitial site). The linewidth of the β-NMR 8Li+ resonance increases dramatically above 150 K, and reaches a maximum at about 290 K. These results are consistent with a site change from an interstitial to a substitutional beginning at ~150 K. The field dependence of the linewidth at 100 K is also discussed.
10.1016/j.physb.2007.08.160
2006
Title
Early 8Li+ β-NMR investigations in GaAs and Ge
Author
K. H. Chow, Z. Salman, W. A. MacFarlane, B. Campbell, T. A. Keeler, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, G. D. Morris, T. J. Parolin, S. Daviel, Z. Yamani
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
415-418
Year
2006
Abstract
In this paper, we describe initial studies of the structure and dynamics associated with 8Li+ in bulk crystalline GaAs and Ge. At low temperatures in GaAs, the amplitude of the 8Li+ resonance signal at ~3 T indicates that a large fraction (at least 70 %) of the Li end up in locations with cubic symmetry (i.e. the tetrahedral interstitial and substitutional sites). The linewidth of the β-NMR resonance increases dramatically above 150 K, reaches a maximum at about 290 K, and decreases again. This suggests that the Li starts to change its location, probably from an interstitial to a substitutional site, at ~150 K. Experiments in Ge are also described. In this sample, a narrow resonance is seen at low temperatures that is likely due to Li located at an interstitial site. Near room temperature, it appears that Li is converting to another site.
10.1016/j.physb.2005.11.120
Title
Beta-detected NQR in zero field with a low energy beam of 8Li+
Author
Z. Salman, R. F. Kiefl, K. H. Chow, W. A. MacFarlane, S. R. Kreitzman, D. J. Arseneau, S. Daviel, C. D. P. Levy, Y. Maeno, R. Poutissou
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
468-471
Year
2006
Abstract
Beta-detected nuclear quadrupole resonances (β-NQR) in zero field are observed using a beam of low energy highly polarized radioactive 8Li+. The resonances were detected in SrTiO3, Al2O3 and Sr2RuO4 single crystals by monitoring the beta-decay anisotropy as a function of a small audio frequency magnetic field. The resonances show clearly that 8Li+ occupies one site with non-cubic symmetry in SrTiO3, two in Al2O3 and three sites in Sr2RuO4. The resonance amplitude and width are surprisingly large compared to the values expected from transitions between the |±2> ↔ |±1> spin states, indicating a significant mixing between the |±m> quadrupolar split levels.
10.1016/j.physb.2005.11.168
arXiv:cond-mat/0511356 [cond-mat.str-el]
Title
β-detected NMR of 8Li in the normal state of 2H-NbSe2
Author
D. Wang, M. D. Hossain, Z. Salman, D. Arseneau, K. H. Chow, S. Daviel, T. A. Keeler, R. F. Kiefl, S. R. Kreitzman, C. D. P. Levy, G. D. Morris, R. I. Miller, W. A. MacFarlane, T. J. Parolin, H. Saadaoui
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
239-242
Year
2006
Abstract
β-NMR of isolated 8Li has been investigated in the normal state of 2H-NbSe2. In a high magnetic field of 3 T a single resonance is observed with a Gaussian line width of 3.5 kHz. The line shape varies weakly as function of magnetic field and temperature but has a strong orientation dependence. The nuclear electric quadrupole splitting is unresolved implying that the electric field gradients are 10-100 times smaller than in other non-cubic crystals. The nuclear spin relaxation rate is also anomalously small but varies linearly with temperature as expected for Korringa relaxation in a metal. These results suggest that Li adopts an interstitial position between the weakly coupled NbSe2 layers and away from the conduction band.
10.1016/j.physb.2005.11.064
arXiv:cond-mat/0511357 [cond-mat.str-el]
Title
Hyperfine fields in a Ag/Fe magnetic multilayer probed with low energy spin polarized 8Li
Author
T. A. Keeler, Z. Salman, K. H. Chow, B. Heinrich, M. D. Hossain, B. Kardasz, R. F. Kiefl, S. R. Kreitzman, W. A. MacFarlane, O. Mosendz, T. J. Parolin, D. Wang
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
79-82
Year
2006
Abstract
A beam of low energy 8Li has been used to probe the hyperfine field distribution in a magnetic multilayer composed of Au(4 nm)/Ag(80 nm)/Fe(2 nm) grown on a GaAs substrate. The β-NMR frequency spectrum is shown to be a strong function of the implantation energy reflecting the depth dependence of the local hyperfine fields. Correlating the spectra with TRIM.SP implantation profiles allows us to identify signals from the GaAs, Ag and Au layers. The frequency spectrum in Ag is a strong function of energy. A very narrow line, and corresponding distribution of hyperfine fields, is observed when the beam in centered well away from the Fe whereas a much broader distribution is observed when the Li stops close to the Fe. These results demonstrate that low energy β-NMR can act as a sensitive probe of the induced magnetism in the otherwise non-magnetic Ag spacer layers.
10.1016/j.physb.2005.11.020
Title
β-NMR of palladium foil
Author
T. J. Parolin, Z. Salman, J. Chakhalian, D. Wang, T. A. Keeler, M. D. Hossain, R. F. Kiefl, K. H. Chow, G. D. Morris, R. I. Miller, W. A. MacFarlane
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
419-422
Year
2006
Abstract
Beta-detected NMR (β-NMR) of low-energy implanted 8Li+ was studied in metallic palladium. The resonance was found to have a large negative shift with respect to the reference signal in the cubic insulator MgO. This shift exhibited significant temperature dependence on cooling below room temperature, approximately proportionate to the temperature-dependent spin susceptibility of pure Pd. Thus it is tentatively attributed to a Knight shift (K) caused by a large negative hyperfine coupling; a phenomenon common in transition metal ions, but not in alkalis. However, the spin-lattice relaxation of 8Li is much slower than expected from the Korringa law for such a large K. We compare results from samples of very different thicknesses: 12.5 μm foil and a 100 nm thin film.
10.1016/j.physb.2005.11.121
Title
Nuclear spin relaxation of 8Li in a thin film of La0.67Ca0.33MnO3
Author
R. I. Miller, D. Arseneau, K. H. Chow, S. Daviel, A. Engelbertz, M. D. Hossain, T. Keeler, R. F. Kiefl, S. Kreitzman, C. D. P. Levy, P. Morales, G. D. Morris, W. A. MacFarlane, T. J. Parolin, R. Poutissou, H. Saadaoui, Z. Salman, D. Wang, J. Y. T. Wei
Journal
Physica B: Condensed Matter
Volume
374-375
Pages
30-33
Year
2006
Abstract
We report β-NMR measurements of the nuclear spin relaxation rate in a thin film of La0.67Ca0.33MnO3 (LCMO) using a low-energy beam of spin-polarized 8Li. In a small magnetic field of 150 G, there is a broad peak in 1/T1 near the Curie temperature (Tc = 295 K) and a dramatic decrease in 1/T1 at lower temperatures. This is attributed to a critical slowing down of the spin fluctuations near Tc and freezing of the magnetic excitations at low temperatures, respectively. In addition, there is a small amplitude, slow relaxing component at high temperatures, which we attribute to 8Li in the SrTiO3 substrate. There is an indication that the spin relaxation rate in the substrate is also peaked at Tc due to close proximity to the magnetic film. These results establish that low-energy β-NMR can be used as a probe of magnetic fluctuations in magnetic thin films over a wide range of temperatures.
10.1016/j.physb.2005.11.009
2004
Title
β-ray Angular Distribution from Purely Nuclear Spin Aligned 20Na
Author
K. Minamisono, K. Matsuta, T. Minamisono, C. D. P. Levy, T. Nagatomo, M. Ogura, T. Sumikama, J. A. Behr, K. P. Jackson, H. Fujiwara, M. Mihara, M. Fukuda
Journal
Hyperfine Interactions
Volume
159
Issue
1-4
Pages
265-268
Year
2004
Abstract
The alignment correlation term in the β-decay angular distribution from purely nuclear spin aligned 20Na has been measured for the first time. The final objective is to test the G parity symmetry, one of the fundamental symmetry in the weak nucleon current. For artificial creation of the alignment, the knowledge of the hyperfine interaction of 20Na implanted in a single-crystal ZnO was utilized.
10.1007/s10751-005-9108-1
Title
Production of Nuclear Polarization of Na Isotopes at ISAC/TRIUMF and its Hyperfine Interaction
Author
K. Minamisono, K. Matsuta, T. Minamisono, C. D. P. Levy, T. Nagatomo, M. Ogura, T. Sumikama, J. A. Behr, K. P. Jackson, H. Fujiwara, M. Mihara, M. Fukuda
Journal
Hyperfine Interactions
Volume
159
Issue
1-4
Pages
261-264
Year
2004
Abstract
Hyperfine interactions of Na isotopes in single crystals have been studied using highly nuclear polarized 20,21,26,27,28Na beams provided by ISAC/TRIUMF. The degree of polarization kept in the crystals, the spin-lattice relaxation times, the electric quadrupole coupling constants and the initial distribution of the populations were measured. Such knowledge is indispensable for the application of the hyperfine interactions in the study of precision measurements such as the nuclear structure through nuclear moments and the fundamental symmetries.
10.1007/s10751-005-9107-2
2003
Title
The new β-NMR facility at TRIUMF and applications in semiconductors
Author
K. H. Chow, Z. Salman, R. F. Kiefl, W. A. MacFarlane, C. D. P. Levy, P. Amaudruz, R. Baartman, J. Chakhalian, S. Daviel, Y. Hirayama, A. Hatakeyama, D. J. Arseneau, B. Hitti, S. R. Kreitzman, G. D. Morris, R. Poutissou, E. Reynard
Journal
Physica B: Condensed Matter
Volume
340-342
Pages
1151-1154
Year
2003
Abstract
A new facililty for conducting beta-detected nuclear magnetic resonance (β-NMR) investigations of condensed matter systems has recently been constucted at TriUniversity Meson Facility in Vancouver, Canada. The unique features of this new facility are described, and some preliminary results on 8Li+ in GaAs are presented.
10.1016/j.physb.2003.09.101
Title
Polarized radioactive beam at ISAC
Author
C. D. P. Levy, A. Hatakeyama, Y. Hirayama, R. F. Kiefl, R. Baartman, J. A. Behr, H. Izumi, D. Melconian, G. D. Morris, R. Nussbaumer, M. Olivo, M. Pearson, R. Poutissou, G. W. Wight
Journal
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Volume
204
Pages
689-693
Year
2003
Abstract
The polarized beam line at ISAC relies on the well known technique of collinear optical pumping to polarize the nuclear spins of a low energy (10-60 keV) radioactive beam. Alkali-metal beams are longitudinally polarized by optical pumping of a fast atomic beam, which is created by charge exchange of the incident ion beam in a Na vapour cell. At ISAC, the beam is then reionized in a He gas target and directed to the experiments. To date, 30 keV beams of 8Li and 9Li have been polarized, and 11Li and 20Na beams are scheduled immediately following this conference. The polarization of the 8Li beam, using a dual frequency, standing wave Ti:sapphire laser, is up to ~80 %. High polarization is achieved by matching the laser bandwidth to the energy spread in the beam. The status of the facility is reported.
10.1016/S0168-583X(03)00485-3
Title
Low energy spin polarized radioactive beams as a probe of thin films and interfaces
Author
R. F. Kiefl, W. A. MacFarlane, P. Amaudruz, D. Arseneau, R. Baartman, T. R. Beals, J. Behr, J. Brewer, S. Daviel, A. Hatakeyama, B. Hitti, S. R. Kreitzman, C. D. P. Levy, R. Miller, M. Olivo, R. Poutissou, G. D. Morris, S. R. Dunsiger, R. Heffner, K. H. Chow, Y. Hirayama, H. Izumi, C. Bommas, E. Dumont, L. H. Greene
Journal
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Volume
204
Pages
682-688
Year
2003
Abstract
A spectrometer for β-detected nuclear magnetic resonance (β-NMR) has been commissioned at the ISAC facility at TRIUMF. A beam of low energy highly spin polarized 8Li+ can be decelerated and implanted into ultra-thin structures 6-400 nm thick. β-NMR provides local information on the electronic and magnetic properties of materials which is similar to conventional NMR but can be used as a sensitive probe of ultra-thin films, interfaces and other nanostructures. We report here on the status of the spectrometer and preliminary results on a simple metal film.
10.1016/S0168-583X(03)00479-8
Title
8Li β-NMR in thin metal films
Author
W. A. MacFarlane, G. D. Morris, T. R. Beals, K. H. Chow, R. A. Baartman, S. Daviel, S. R. Dunsiger, A. Hatakeyama, S. R. Kreitzman, C. D. P. Levy, R. I. Miller, K. M. Nichol, R. Poutissou, R. F. Kiefl
Journal
Physica B: Condensed Matter
Volume
326
Issue
1-4
Pages
213-216
Year
2003
Abstract
We have measured the temperature dependence of the β-NMR resonances of 8Li implanted in thin films of Au and Ag. At room temperature single narrow resonances are observed. The absence of appreciable quadrupolar splitting or broadening indicates that the Li is isolated and at a site of cubic symmetry. As the temperature is lowered, a second resonance appears which is shifted higher in frequency by ~100 ppm. We attribute the two lines to two distinct cubic sites with slightly different Knight shifts and discuss the application of this result to study fundamental phenomena exhibited by nano-confined metallic electrons.
10.1016/S0921-4526(02)01604-6
Title
Quadrupolar split 8Li β-NMR in SrTiO3
Author
W. A. MacFarlane, G. D. Morris, K. H. Chow, R. A. Baartman, S. Daviel, S. R. Dunsiger, A. Hatakeyama, S. R. Kreitzman, C. D. P. Levy, R. I. Miller, K. M. Nichol, R. Poutissou, E. Dumont, L. H. Greene, R. F. Kiefl
Journal
Physica B: Condensed Matter
Volume
326
Issue
1-4
Pages
209-213
Year
2003
Abstract
We have measured the temperature dependence of the β-NMR resonances of 8Li+ implanted in the top few thousand of a crystal of SrTiO3 in a magnetic field of 3 T || <100>. A well-resolved quadrupolar splitting of the resonance is observed indicating a noncubic Li site with symmetry <100> and a quadrupolar frequency νQ(211 K) = 153.2(4) kHz. The cubic-to-tetragonal phase transition is reflected in the linewidths demonstrating that β-NMR is a sensitive probe of the structure near a surface.
10.1016/S0921-4526(02)01603-4
Title
Low-energy spin-polarized radioactive beams as a nano-scale probe of matter
Author
R. F. Kiefl, W. A. MacFarlane, G. D. Morris, P. Amaudruz, D. Arseneau, H. Azumi, R. Baartman, T. R. Beals, J. Behr, C. Bommas, J. H. Brewer, K. H. Chow, E. Dumont, S. R. Dunsiger, S. Daviel, L. Greene, A. Hatakeyama, R. H. Heffner, Y. Hirayama, B. Hitti, S. R. Kreitzman, C. D. P. Levy, R. I. Miller, M. Olivo, R. Poutissou
Journal
Physica B: Condensed Matter
Volume
326
Issue
1-4
Pages
189-195
Year
2003
Abstract
We have commissioned a polarized low-energy 8Li ion beam line, which together with a high-field β-NMR spectrometer, can act as sensitive new probe of thin films and interfaces. The implantation energy can be continuously adjusted from 1 to 90 keB and the maximum polarization achieved thus far is 80 %. This instrument opens up new applications for β-NMR which parallel and complement efforts with low-energy muons. For example, it is possible to probe the magnetic field distribution near the surface of a material by stopping a polarized 8Li beam in a thin overlayer of Ag. Since the 8Li adopts a site with cubic symmetry in Ag there is no quadrupolar splitting of the resonance, and the 8Li acts as a purely magnetic sensor.
10.1016/S0921-4526(02)01600-9
Title
Range straggling of low energy 8Li+ in thin metallic films using β-NMR
Author
T. R. Beals, R. F. Kiefl, W. A. MacFarlane, K. M. Nichol, G. D. Morris, C. D. P. Levy, S. R. Kreitzman, R. Poutissou, S. Daviel, R. A. Baartman, K. H. Chow
Journal
Physica B: Condensed Matter
Volume
326
Issue
1-4
Pages
205-208
Year
2003
Abstract
Recently it has been demonstrated that low energy spin polarized radioactive nuclei can be used to probe the electronic and magnetic properties of ultra-thin samples using β detected NMR. However, use of the technique requires an accurate understanding of ion penetration depth and range straggling as a function of beam implantation energy and target density. Range straggling measurements of 8Li were conducted with thin films of metallic Al and Au on sapphire and SrTiO3 substrates and the results were compared to SRIM code predictions.
10.1016/S0921-4526(02)01602-2
2002
Title
A polarized beams project at ISAC
Author
C. D. P. Levy, R. Baartman, K. Jayamanna, R. Kiefl, T. Kuo, M. Olivo, G. W. Wight, D. Yuan, A. N. Zelenski
Journal
Nuclear Physics A
Volume
701
Issue
1-4
Pages
253-258
Year
2002
Abstract
A polarizer beam line at the radioactive beams facility ISAC at TRIUMF is nearly complete. Initially for 8Li+ ions for β-NMR studies in condensed matter, it can in principle supply three or more experiments simultaneously, and the technique used is practicable with all alkali-metal ion beams. An atomic beam, created with over 90 % efficiency by passing the initial unpolarized 30 keV beam through a sodium vapor jet target, will be polarized by colinear optical pumping. A novel feature is that the atomic beam is reionized with demonstrated high efficiency in a helium gas target. The emittance growth through the helium cell has been measured for stable 7Li+ beam on a test stand and found to be small. We report these measurements as a function of helium flow rates. A preliminary polarized 8Li+ run is planned for May, 2000.
10.1016/S0375-9474(01)01593-7
2000
Title
Complementarity of low-energy spin polarized radioactive nuclei and muons
Author
R. F. Kiefl, G. D. Morris, P. Amaudruz, R. Baartman, J. Behr, J. H. Brewer, J. Chakhalian, S. Daviel, J. Doornbos, S. Dunsiger, S. R. Kreitzman, T. Kuo, C. D. P. Levy, R. Miller, M. Olivo, R. Poutissou, G. W. Wight, A. Zelenski
Journal
Physica B: Condensed Matter
Volume
289-290
Pages
640-647
Year
2000
Abstract
The recently completed ISAC facility at TRIUMF is the most intense source of low-energy radioactive ions in the world. Beams of short-lived radioactive ions have applications in many different areas of physics including condensed matter research. At ISAC we are developing the technique of beta-detected nuclear magnetic resonance (β-NMR) as a tool for investigating thin structures and dilute impurities. Large nuclear spin polarization can be generated using a fast collinear laser method so that a beam of highly spin polarized ions can be implanted at low energies (1-90 keV). In this paper we describe the facility and the initial experimental program with emphasis on how this technique can complement μSR.
10.1016/S0921-4526(00)00301-X

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