Theses

To date, 11 theses using the β-NMR technique at TRIUMF have been written. They are listed below in reverse chronological order.

2021

Title: Finite size effects in strongly correlated transition metal oxides probed by β-detected NMR
Author: V. L. Karner
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2021
Abstract: In this thesis, the strongly correlated metal LaNiO₃ was studied in bulk and heterostructures using ⁸Li β-NMR. The main objective of the thesis was to probe the metallic state and how it changes on approach to a dimensionality-induced metal-insulator transition (MIT) in heterostructures. With its sensitivity to the metallic state, akin to conventional NMR, and ability to study thin films and heterostructures, ⁸Li β-NMR is uniquely suited to tackle this challenging subject.
In bulk LaNiO₃, spin-lattice relaxation (SLR) measurements reveal two equally abundant components with linear temperature dependence below 200 K. The linearity is consistent with a Korringa mechanism and is evidence of a conventional metallic state. The resonance is characterized by a single broad line with a small temperature independent Knight shift. The normalized Korringa product indicates substantial antiferromagnetic correlations.
In LaNiO₃ heterostructures with insulating LaAlO₃, an MIT and Néel order has been observed when the thickness of LaNiO₃ is reduced to 2 u.c.. We used ⁸Li β-NMR to study heterostructures with varying thicknesses of LaNiO₃. SLR measurements show two equally abundant components with distinct temperature dependences. One component is linear with temperature, and only weakly affected by LaNiO₃ thickness. In contrast, the second component is non-linear, and strongly depends on thickness. We attribute the two component relaxation in the heterostructures and bulk LaNiO₃ to microscopic phase separation of the electronic state.
Finally, we studied some novel LaNiO₃ heterostructures where LaAlO₃ was replaced with the magnetic insulator La₂CuO₄. Bulk La₂CuO₄ is characterized by long-range antiferromagnetic order below T_N ≈ 300 K which is extremely sensitive to doping. In a La₂CuO₄ film, SLR measurements reveal fast but measurable 1/T₁. We see evidence of magnetic order not from a peak in 1/T₁ but instead by a gradual loss of asymmetry beginning at 140 K. We attribute the suppression of T_N and the broad transition to inhomogeneous hole doping in the film. Below 40 K, an upturn in 1/T₁ suggests freezing of mobile holes from the more doped regions of the sample. The behavior in the heterostructures is similar to the La₂CuO₄ film.
: 10.14288/1.0402656
: https://hdl.handle.net/2429/80103

Title: The interfacial dynamics of amorphous materials as revealed by β-NMR measurements and molecular simulations
Author: D. J. Fujimoto
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2021
Abstract: The free surface is important for developing a fundamental understanding of dynamical length scales in glasses. We first investigate the relaxation of freestanding atactic polystyrene (aPS) thin films with molecular dynamics simulations. As in previous coarse-grained simulations, the surface modification on the relaxation times for backbone segments and phenyl rings may be expressed as a power law relation, wherein the bulk dynamics fully encapsulate the temperature-dependence. Variation of the coupling exponent with distance from the surface is consistent with depth-dependent activation barriers. We also quantify a reduction of dynamical heterogeneity, transient spatial fluctuations of the dynamics, at the interface which can be interpreted in the framework of cooperative models for glassy dynamics.
Capable of depth-resolved measurements near the surface, implanted-ion beta-detected nuclear magnetic resonance (β-NMR) has been a powerful technique for the study of dynamics in aPS thin films. We have completed and commissioned an upgrade to the β-NMR spectrometer, extending the accessible upper temperature, and enabling a direct comparison between this experimental technique and the molecular dynamics simulations. We demonstrate that the modified spectrometer is now capable of operation to at least 400 K, an improvement of more than 80 K.
We also demonstrate the application of β-NMR as a probe of ionic liquid molecular dynamics through the measurement of ⁸Li⁺ spin-lattice relaxation (SLR) and resonance in 1-ethyl-3-methylimidazolium acetate. The motional narrowing of the resonance, and the local maxima in the SLR rate, 1/T₁, imply a sensitivity to sub-nanosecond Li⁺ solvation dynamics. From an analysis of 1/T₁, we extract an activation energy and Vogel-Fulcher-Tammann constant in agreement with the dynamic viscosity of the bulk solvent. Near the melting point, the lineshape is broad and intense, and the form of the relaxation is non-exponential, reflective of our sensitivity to heterogeneous dynamics near the glass transition. We also employ the depth resolution capabilities of this technique to probe the subsurface dynamics with nanometer resolution. We show modified dynamics near the surface in, and above, the glassy state.
: 10.14288/1.0401227
: https://hdl.handle.net/2429/79192

2020

Title: Microscopic dynamics of isolated lithium in crystalline solids revealed by nuclear magnetic relaxation and resonance of ⁸Li
Author: R. M. L. McFadden
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2020
Abstract: This thesis reports measurements on the dynamics of isolated lithium in single crystal materials using ion-implanted ⁸Li β-detected nuclear magnetic resonance. From spin-lattice relaxation and resonance measurements, we identify the kinetic parameters describing the ion’s site-to-site hop rate – the elementary process in long-range solid-state diffusion – and compare the results with theoretical work in the literature, as well as experiments at higher concentration. In addition to these "ionic" details, the nuclear magnetic resonance probe provides information on the electronic properties of the host, whose most intriguing features are also discussed.
In the one-dimensional ion conductor rutile TiO₂, we find two sets of thermally activated dynamics: one below 100 K and another at higher temperatures. We suggest the low temperature process is unrelated to lithium motion, but rather a consequence of electron polarons in the vicinity of the implanted ⁸Li⁺. Above 100 K, Li⁺ undergoes diffusion as an isolated uncomplexed cation, characterized by an activation energy and prefactor that are in agreement with macroscopic diffusion measurements, but not with theory.
In Bi₂Te₂Se, a topological insulator with layered tetradymite structure, implanted ⁸Li⁺ undergoes ionic diffusion above 150 K, likely in the van der Waals gap between adjacent Te planes. A comparison with structurally related materials reveals the mobility of isolated Li⁺ is exceptional. At lower temperature, we find linear Korringa-like relaxation, but with a field dependent slope and intercept, accompanied by an anomalous field dependence to the resonance shift. We suggest that these may be related to a strong contribution from orbital currents or the magnetic freezeout of charge carriers in this heavily compensated semiconductor.
In the doped tetradymite topological insulators Bi₂Se₃:Ca and Bi₂Te₃:Mn, the onset of lithium dynamics is suppressed to above 200 K. At low temperatures, the nuclear magnetic resonance properties are those of a heavily doped semiconductor in the metallic limit, with Korringa relaxation and a small, negative, temperature-dependent Knight shift. From this, we make a detailed comparison with isostructural Bi₂Te₂Se.
: 10.14288/1.0389972
: https://hdl.handle.net/2429/74167

Title: Diffusion and surface trapping of ⁸Li in rutile TiO₂ and the comparison on ⁸Li and ⁹Li spin relaxation using β-NMR
Author: C. A. Chatzichristos
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2020
Abstract: It is well established that the properties of many materials change as their thickness is shrunk to the nanoscale, often yielding novel features at the near-surface region that are absent in the bulk. Even though there are several techniques that can study either the bulk or the surface of these materials, there are very few that can scan the near-surface region of crystals and thin films versus depth. Beta-detected NMR (β-NMR) is capable of this and therefore has been established as a powerful tool for material science. This thesis aims to further develop the capabilities of β-NMR.
The first part of this thesis demonstrates that by comparing the spin-lattice relaxation rates (SLR) of two radioactive Li isotopes (^8,9Li) it is possible to distinguish whether the source of SLR in a given situation is driven by magnetic or electric interactions. This is an important development for β-NMR, since there are instances where it is problematic to distinguish whether the measured relaxation is due to magnetic or electric fluctuations. Using this method, it was found that the SLR in Pt is (almost) purely magnetic in origin, whereas the spin relaxation in SrTiO₃ is driven (almost) entirely by electric quadrupolar interactions.
The second part of this thesis traces the development of α-radiotracer, that uses the progeny α-particles from the decay of ⁸Li, in order to directly measure the nanoscale diffusivity of Li⁺ in Li-ion battery materials. To develop this technique, Monte Carlo simulations of the experimental configuration were carried out, a new apparatus and a new α-detector were designed and used for experiments on rutile TiO₂. In rutile, the measurements revealed that Li⁺ gets trapped at the (001) surface, a result that helps explain the suppressed intercalation of Li⁺ in bulk rutile. Moreover, the diffusion rate of Li⁺ in rutile was found to follow a bi-Arrhenius relationship, with a high-T activation energy in agreement with other reported measurements and a low-T component of similar magnitude with the theoretically calculated diffusion barrier as well as the activation energy of the Li-polaron complex found with β-NMR below 100 K.
: 10.14288/1.0388862
: https://hdl.handle.net/2429/73678

2018

Title: Synthesis and electronic ordering phenomena of calcium ruthenate thin films
Author: C. J. Dietl
Degree: PhD
School: University of Stuttgart
Address: Stuttgart
Year: 2018
Abstract: The prospect to harness the wide range of electronic phenomena foundin transition metal oxides by synthesizing thin film structures and their implementation into next-generation technologies has sparked a research activity of ever increasing pace. Most prominent are thin film techniques such as heterostructuring and strain engineering, whichhave been shown to open up new paths to study the rich physics in these compounds.
This work constitutes a study of the thin film synthesis of the layered orthorhombic transition metal oxide compound Ca₂RuO₄ (CRO) and of the impact of biaxial epitaxial strain on the magnetic and orbital ordering phenomena previously found by spectroscopic methods. The electronic structure of CRO and other transition metal oxides with 4d-valence electrons is of significant topical interest, because the energy scales of spin-orbit-coupling, exchange energy and crystal field are comparable. As a result, the antiferromagnetic Mott insulator CRO plays host to an array of novel ground states and is highly susceptible to external perturbations as has been shown by numerous studies on single crystals involving e.g pressure, chemical substitutionand electrical current.
Embarking on the strategy to exploit this sensitivity of CRO, we employ strain engineering via thin film growth to tune its properties. The details of the synthesis route using pulsed laser deposition arepresented. Growth was accomplished with two distinct sets of high-quality samples - a-axis oriented films on LaSrAlO₄ and NdCaAlO₄ substrates with (110) cut and c-axis oriented films on LaAlO₃, LaSrAlO₄ and YAlO₃ substrates with (001) cut. Structural characterization shows that the epitaxy exerts strains of 1%–3% on the lattice constants of CRO compared to the bulk system. These large distortions manifest themselves in the electrical transport properties, which shows that the electronic state can be profoundly tuned froman insulator to a metal.
Comprehensive resonant elastic X-ray scattering and magnetometry studies confirm the presence of antiferromagnetism in CRO on LaAlO₃, NdCaAlO₄ and LaSrAlO₄ (110) at T_N = 150 K, similar to the antiferromagnetic state found in bulk. Detailed polarization analysis of resonant peaks reveals a b-axis oriented magnetic moment for CRO on LaSrAlO₄ (110), as found in bulk. On the other side, CRO on NdCaAlO₄ shows an unusual signal that is compatible with a magnetic moment 45^◦ away from the c-axis, approximately along the (102) direction of the orthorhombic unit cell of CRO, which has not been reported for the bulk system. Furthermore, magnetoresistance and magnetometry measurements show a weak ferromagnetic signal along the c-axis within the antiferromagnetic phases. We show that, while a moment direction along the b-axis is compatible with a representation analysis of the bulk Pbca space group, the presence of a weak ferromagnetic component along the c-axis and the peculiar magnetic moment direction along the (102) for CRO on NdCaAlO₄ cannot be described by a single irreducible representation of the space group Pbca. Thus, we suggest either an exotic scenario with more than one critical irreducible representation or that the thin films exhibit anunusual symmetry reduction from the bulk space group Pbca. The finding of a strain-induced moment direction switching points to a non-trivial effect of epitaxial strain on the magnetic interactions inCRO.
Magnetometry, magnetoresistance and polarized neutron reflectometry experiments were conducted to investigate a low-temperature ferromagnetic phase in the c-axis oriented samples. Similar to pressurized bulk, we find ferromagnetic moment amplitudes of the order 0.1 μ_B/Ru and an enhancement under compressive strain. Polarized neutron reflectometry was used to exclude impurity phases or surface effects as the underlying mechanism. Analogous to the pressurized bulk system, we found a giant positive magnetoresistance in CRO on LaAlO₃.
Moreover, a combined nuclear magnetic resonance and resonant elastic X-ray scattering study was dedicated to study the impact ofepitaxial strain on quadrupolar order previously found in bulk CRO. Due to the small mass of the thin films, the nuclear magnetic resonance experiments were conducted using the βNMR-technique, which detects the spin lattice relaxation through the asymmetry of the β-decay of highly-polarized ⁸Li-isotopes. The temperature dependenceof the relaxation rate of the c-axis oriented films showed an increase towards higher temperatures, starting at ~200 K. More detailed measurements on metallic CRO on LaSrAlO₄ (001) revealed an anomaly at 300 K, which is reminiscent of a phase transition. Since resonant X-ray scattering on bulk CRO showed orbital ordering phenomena in the same temperature range, we similarly searched for quadrupolar ordering using synchrotron radiation tuned to the Ru-L absorption edges. However, the resonant peaks detected in our experiments could be fully described by Templeton scattering, a phenomenon arising from purely structural effects. For reference purposes, we performed a similar analysis for the single crystal showing that the results previously interpreted as antiferro-orbital order bear many signatures of Templeton scattering as well. Thus, this work motivates a reevaluation of the original scattering study. An alternative scenario for the βNMR anomaly based on diffusion of the ⁸Li-ions is discussed.
The synthesis of CRO on a variety of substrates enables furtherstudies of the influence of large structural distortions on the electronic states in CRO, which are currently inaccessible by pressuretechniques for single crystals. This opens up new opportunities to test theories regarding the electronic states in CRO, which are intensively debated due to multiple competing energy scales. Specifically, arecently proposed strong spin-orbit coupling picture for CRO predictsa high sensitivity towards the crystal field splitting in this material, which is directly tuned via the epitaxial strain. The large tunabilityof the electronic properties CRO by epitaxial strain might be usefulfor future thin film devices
: 10.18419/opus-10069
: https://elib.uni-stuttgart.de/handle/11682/10086

2012

Title: β-Detected NMR of ⁸Li⁺ in spintronic materials
Author: Q. Song
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2012
Abstract: β-detected Nuclear Magnetic Resonance (βNMR) employs radioactive ⁸Li⁺, which is optically spin-polarized, as a local probe to study magnetism in materials via β decay. In this thesis, βNMR is applied to spintronic materials, including GaAs, Ga_1-xMn_xAs and Fe/GaAs heterostructures in a depth-controlled manner at TRIUMF.
High resolution β-NMR measurements were carried out on GaAs crystals (semi-insulating (SI-GaAs) and heavily doped n-type (n-GaAs)) as a control experiment for β-NMR on Fe/GaAs heterostructures. A small resonance shift was observed and found to be dependent on depth, temperature and doping. The depth dependence is only observed in SI-GaAs and not in n-GaAs. The resonance shift below 150 K in both GaAs is ~100 ppm, on the same order of some Knight shifts of ⁸Li⁺ in noble metals.
Ga_1-xMn_xAs is the first βNMR study on a ferromagnetic material through the ferromagnetic transition. Both spin lattice relaxation (SLR) and resonance of ⁸Li⁺ were measured. Two resonances were clearly resolved from the nonmagnetic GaAs substrate and the magnetic Ga_1-xMn_xAs film. The latter one negatively shifts and is linearly proportional to the applied field. The hyperfine coupling constant A_HF of ⁸Li⁺ in Ga_1-xMn_xAs is found to be negative. The SLR rate λ does not follow Korringa’s Law and its amplitude shows a weak temperature dependence through T_C. The behaviours of A_HF and λ suggest that the delocalized holes originate from a Mn derived impurity band. No evidence of magnetic phase separation is found.
⁸Li⁺ provides a new depth-dependent local probe to detect injected spin polarization. We measured the ⁸Li⁺ resonance in Fe/GaAs heterostructures with semi-insulating and heavily doped n-type substrates, with and without injected current. With zero current, no spin polarization at thermal equilibrium is found. A new current injection system was designed and setup to conduct current injection from the thin Fe layer into the n-GaAs substrate. We found effects of local Joule heating and a very small stray field caused by the injected current but no convincing evidence of injected spin polarization.
: 10.14288/1.0073399
: https://hdl.handle.net/2429/43638

2011

Title: Using low-energy ⁸Li beta-detected NMR to probe the magnetism of transition metals
Author: T. J. Parolin
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2011
Abstract: Low-energy, beta-radiation-detected nuclear magnetic resonance (β-NMR) is applied to probe the magnetism of Au and Pd. The measurements were carried out at the TRIUMF β-NMR facility using optically spin-polarized ⁸Li⁺ as the probe.
The behaviour of ⁸Li⁺ in Au was investigated using samples in the form of a foil and a 100 nm film evaporated onto a MgO (100) substrate. The results are in overall agreement with those obtained previously in Ag, Cu, and Al. Narrow, temperature-independent resonances are observed and assigned to ions stopping in the octahedral interstitial and substitutional lattice sites; the latter appearing only for temperatures above 150 K which is attributed to a thermally-activated site change. The spin-lattice relaxation rate of substitutional site ions is less than half as fast at ambient temperature as that in the other simple metals. The rate is independent of external field for fields greater than 15 mT. A Korringa analysis for the substitutional ions indicates no significant electron enhancement over that of a free electron gas. For all four metals, the enhancements obtained are smaller than those for the host nuclei. No depth dependence was found for the resonances in Au.
The highly exchange-enhanced metal Pd was studied using samples in the form of a foil and a 100 nm film evaporated onto a SrTiO₃ (100) substrate. Strongly temperature-dependent, negative shifts are observed that scale with the temperature dependence of the host susceptibility between room temperature and 110 K. The resonances appear as two partially resolved lines that exhibit similar behaviour with temperature. The linewidths are broad and double upon cooling. The data are indicative of ions stopping in a site of cubic symmetry. The spin-lattice relaxation rate increases linearly with increasing temperature and eventually saturates at higher temperatures, consistent with the prediction from spin fluctuation theory. In contrast to the simple metals, large Korringa enhancements are obtained in this host. Ferromagnetic dynamical scaling is observed to hold above 110 K. Features below this temperature indicate that the Li ions locally induce a further enhancement of the static susceptibility. The temperature dependence of the modified susceptibility is in keeping with the prediction for a weak itinerant ferromagnet just above the Curie temperature; however, there is no evidence of static order.
: 10.14288/1.0062186
: https://hdl.handle.net/2429/39778

2009

Title: Magnetic properties near the surface of cuprate superconductors studied using beta-detected NMR
Author: H. Saadaoui
Degree: PhD
School: University of British Columbia
Address: Vancouver
Year: 2009
Abstract: Beta-detected Nuclear Magnetic Resonance (β-NMR) uses highly spin polarized β-emitting nuclei as a probe. Besides its use in nuclear physics, it has also become a powerful and sensitive tool in condensed matter physics and materials science. At TRIUMF, β-NMR of ⁸Li⁺ has been developed to study materials in a depth-resolved manner, where the implantation depth of ⁸Li⁺ is controlled via electrostatic deceleration. In this thesis, β-NMR of ⁸Li⁺ has been used to study high-T_c cuprate superconductors (HTSC). The objective of this work is to search for spontaneous magnetic fields generated by a possible time-reversal symmetry breaking (TRSB) superconducting state near the surface of hole-doped YBa₂Cu₃O_7-δ (YBCO), and study the nature of the vortex lattice (VL) in YBCO and electron-doped Pr_2-xCe_xCuO_4-δ (PCCO). For several advantages, our measurements were carried out by implanting ⁸Li⁺ in thin silver films evaporated on the superconductors.
In our TRSB studies, the magnetic field distribution p(B) is measured 8 nm away from the Ag/YBCO interface in magnetic fields B₀ = 5 to 100 G, applied parallel to the interface. p(B) showed significant broadening below the T_c of ab- and c-axis oriented YBCO films. The broadening signals the existence of weak disordered magnetic fields near the surface of YBCO. From the broadening's temperature and field dependence we draw an upper limit of 0.2 G on the magnitude of spontaneous magnetic fields associated with TRSB.
To study the VL, p(B) is measured at average implantation depths ranging from 20 to 90 nm away from the Ag/YBCO or Ag/PCCO interface in B₀ = 0.1 to 33 kG, applied perpendicular to the surface. p(B) showed a dramatic broadening below T_c as expected from the emerging field lines of the VL in the superconductor. In YBCO, p(B) is symmetric and the dependence on B₀ is much weaker than expected from an ideal VL, indicating that the vortex density varies across the face of the sample on a long length scale, likely due to vortex pinning at twin boundaries. In PCCO, a 2D VL is established due to the high anisotropy of the superconductor leading to a nearly symmetric p(B).
: 10.14288/1.0068610
: https://hdl.handle.net/2429/17464

2006

Title: Near surface vortex lattice in NbSe₂ studied with low energy beta-NMR
Author: D. Wang
Degree: MSc
School: University of British Columbia
Address: Vancouver
Year: 2006
Abstract: In this thesis, the magnetic field distribution in the vortex state of NbSe₂ is investigated with the technique of depth resolved β-detected NMR using a beam of highly polarized ⁸Li produced at the TRIUMF ISAC facility. The β-NMR lineshape is a direct measure of the local magnetic field distribution weighted according to the implantation profile of the ⁸Li beam. By varying the implantation energy between 1 ~ 30 keV, one can control the average implantation depth corresponds in a range between 5 ~ 136 nm. Above T_c = 7.0 K a relatively narrow resonance is observed whose width is attributed to magnetic dipolar broadening from the ⁹³Nb nuclear moments. Below T_c a much broader asymmetric lineshape is observed, which is characteristic of a triangular magnetic vortex lattice. Modeling the magnetic field distribution allows one to determine both the effective in plane penetration depth λ_|| and the effective in plane coherence length ξ_|| or vortex core radius.
In a magnetic field of 302 mT, we obtain λ_|| = 279(30) nm and ξ_|| = 12(1) nm. In a smaller magnetic field of 10.84 mT, the effective coherence length increases dramatically to a value of 77(10) nm. This is more than an order of magnitude larger than the expected from the coherence length in NbSe₂. The origin of the giant vortices is discussed. We propose an explanation involving the multiband nature of NbSe₂.
: 10.14288/1.0085246
: https://hdl.handle.net/2429/18344

Title: Measurement of the London penetration depth in the Meissner state of NbSe₂ using low energy polarized ⁸Li
Author: M. M. Hossain
Degree: MSc
School: University of British Columbia
Address: Vancouver
Year: 2006
Abstract: In this thesis, the Meissner state of NbSe₂ was investigated using low energy beam of spin polarized ⁸Li. The ⁸Li nuclear spin relaxation rate 1/T₁ was measured as a function of temperature and magnetic field. The spin relaxation rate is sensitive to low frequency nuclear spin dynamics of the host Nb spins and is strongly field dependent. This is used to determine the reduction in the magnetic field upon cooling into the Meissner state. Using a calculated implantation profile and a model field distribution, one can extract a measure of the absolute value of the London penetration depth λ in Meissner state. In addition, a model field distribution, assuming a suppression of order parameter near surface, was developed. In this case, we can extract another length scale which is related to the "coherence" length ξ. The value of λ depends on the model field distribution but is significantly longer than that obtained previously in the vortex state using μSR. From the measured internal magnetic field distribution, London penetration λ_L is extracted as a function of temperature. There is also evidence of the coherence peak in 1/T₁ of host nuclear spins. λ_L(T) follows the two-fluid model of superconductivity. Depending on the model for internal field distribution, λ_L(0) varies in the range (1795-2434) Å.
: 10.14288/1.0092663
: https://hdl.handle.net/2429/17846

Title: Hyperfine magnetic fields in Fe/Ag magnetic multilayers probed with low energy spin polarized ⁸Li
Author: T. A. Keeler
Degree: MSc
School: University of British Columbia
Address: Vancouver
Year: 2006
Abstract: This thesis is a presentation of experiments examining the induced hyperfine magnetism in the nonmagnetic layers of two thin film magnetic multilayers, Au(40 Å)/Ag(200 Å)/Fe(140 Å) and Au(40 Å)/Ag(800 Å)/Fe(20 Å) grown on GaAs (001) single crystal substrates. The main technique used in this study was beta-detected nuclear magnetic resonance (βNMR) conducted at TRIUMF laboratories in Vancouver, British Columbia. βNMR makes NMR measurements on radioactive ⁸Li⁺ (τ = 1.21 sec) nuclei that are implanted directly into the sample. Resonant βNMR experiments showed strong induced magnetism in the non-magnetic Ag layer due the magnetic Fe. Comparison of a theoretical model to experimental results on the Au(40 Å)/Ag(200 Å)/Fe(140 Å) sample suggest that the induced hyperfine magnetism decays with distance into the Ag layer from the magnetic/nonmagnetic interface like x^-1.84 from a maximum of ~0.3 T at the magnetic/nonmagnetic interface.
: 10.14288/1.0092912
: https://hdl.handle.net/2429/18291