There is indirect evidence that the dynamics of a polymer near a free surface are enhanced compared with the bulk but there are few studies of how dynamics varies with depth. β-Detected nuclear spin relaxation of implanted ⁸Li⁺ has been used to directly probe the temperature and depth dependence of the γ-relaxation mode, which is due to phenyl rings undergoing restricted rotation, in thin films of atactic deuterated polystyrene (PS-d8) and determine how the depth dependence of dynamics is affected by sample processing, such as annealing, floating on water and the inclusion of a surfactant, and by the presence of a buried interface. The activation energy for the γ-relaxation process is lower near the free surface. Annealing the PS-d8 films and then immersing in water to mimic the floating procedure used to transfer films had negligible effects on the thickness of the region near the free surface with enhanced mobility. Measurements on a bilayer film indicate enhanced phenyl ring dynamics near the buried interface compared with a single film at the same depth. PS-d8 films annealed with the surfactant sodium dodecyl sulfate (SDS) deposited on the surface show enhanced dynamics in the bulk compared with a pure PS-d8 film and a PS-d8 film where the SDS was washed away. There is less contrast between the surface and bulk in the SDS-treated sample, which could account for the elimination of the T_g confinement effect observed in films containing SDS [Chen and Torkelson, Polymer, 2016, 87, 226].

By measuring the prototypical antiferromagnet $\alpha \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$, we show that it is possible to determine the static spin orientation and dynamic spin correlations within nanometers from an antiferromagnetic surface using the nuclear spin polarization of implanted ${}^8{\mathrm{Li}}^{+}$ ions detected with $\beta$-NMR. Remarkably, the first-order Morin spin reorientation in single crystal $\alpha \text{−}{\mathrm{Fe}}_2{\mathrm{O}}_3$ occurs at the same temperature at all depths between 1 and 100 nm from the (110) surface; however, the implanted nuclear spin experiences an increased $1/T_1$ relaxation rate at shallow depths revealing soft-surface magnons. The surface-localized dynamics decay towards the bulk with a characteristic length of $\epsilon =11\pm 1\mathrm{nm}$, closely matching the finite-size thresholds of hematite nanostructures.

We report measurements on the high-temperature ionic and low-temperature electronic properties of the three-dimensional topological insulator ${\mathrm{Bi}}_2{\mathrm{Te}}_2\mathrm{Se}$ using ion-implanted ${}^8\mathrm{Li}\beta$-detected nuclear magnetic relaxation and resonance. With implantation energies in the range $5–28\mathrm{keV}$, the probes penetrate beyond the expected range of the topological surface state, but are still within $250\mathrm{nm}$ of the surface. At temperatures above $\sim 150\mathrm{K}$, spin-lattice relaxation measurements reveal isolated ${}^8\mathrm{Li}^{+}$ diffusion with an activation energy $E_A=0.185\left(8\right)\mathrm{eV}$ and attempt frequency ${\tau }_0^{-1}=8\pm 3\times {10}^{11}{\mathrm{s}}^{-1}$ for atomic site-to-site hopping. At lower temperature, we find a linear Korringa-type relaxation mechanism with a field-dependent slope and intercept, which is 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 freeze-out of charge carriers in this heavily compensated semiconductor, but that conventional theories are unable to account for the extent of the field dependence. Conventional NMR of the stable host nuclei may help elucidate their origin.

A new high field spectrometer has been built to extend the capabilities of the β-detected nuclear magnetic resonance (β-NMR) facility at TRIUMF. This new beamline extension allows β-NMR spectroscopy to be performed with fields up to 200 mT parallel to a sample’s surface (perpendicular to the ion beam), allowing depth-resolved studies of local electromagnetic fields with spin polarized probes at a much higher applied magnetic field than previously available in this configuration. The primary motivation and application is to allow studies of superconducting radio frequency (SRF) materials close to the critical fields of Nb metal, which is extensively used to fabricate SRF cavities. The details of the design considerations and implementation of the ultra-high vacuum (UHV) system, ion optics, and beam diagnostics are presented here. Commissioning of the beamline and spectrometer with radioactive ions are also reported here. Future capabilities and applications in other areas are also described.

We report $\beta$-detected NMR of ion-implanted ${}^8\mathrm{Li}$ in a single crystal and thin film of the strongly correlated metal ${\mathrm{LaNiO}}_3$. Spin-lattice relaxation measurements reveal two distinct local environments, both metallic as evident from $T$-linear Korringa $1/T_1$ below $200\mathrm{K}$ with slopes comparable to other metals. A small approximately temperature-independent Knight shift of $\sim 74\mathrm{ppm}$ is observed, yielding a normalized Korringa product characteristic of substantial antiferromagnetic correlations. We find no evidence for a magnetic transition from 4 to $310\mathrm{K}$. The similarity of these features in the two very different samples indicates that they are intrinsic and unrelated to dilute oxygen vacancies. We attribute the two environments to two distinct but similar crystallographic ${}^8\mathrm{Li}$ sites and not to any form of phase inhomogeneity, but this is inconsistent with the conventional rhombohedral structure of ${\mathrm{LaNiO}}_3$, and also cannot be simply explained by the common alternative orthorhombic or monoclinic distortions.