Browsing by Author "Dehn, MH"

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    Local metallic and structural properties of the strongly correlated metal LaNiO3 using 8Li β–NMR
    (American Physical Society, 2019-10-07) Karner, VL; Chatzichristos, A; Cortie, DL; Dehn, MH; Foyevtsov, O; Foyevtsova, K; Fujimoto, D; Kiefl, RF; Levy, CDP; Li, R; McFadden, RML; Morris, GD; Pearson, MR; Stachura, M; Ticknor, JO; Cristiani, G; Logvenov, G; Wrobel, F; Keimer, B; Zhang, J; Mitchell, JF; MacFarlane, WA
    We report β-detected NMR of ion-implanted Li8 in a single crystal and thin film of the strongly correlated metal LaNiO3. Spin-lattice relaxation measurements reveal two distinct local environments, both metallic as evident from T-linear Korringa 1/T1 below 200K with slopes comparable to other metals. A small approximately temperature-independent Knight shift of ∼74ppm is observed, yielding a normalized Korringa product characteristic of substantial antiferromagnetic correlations. We find no evidence for a magnetic transition from 4 to 310K. 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 Li8 sites and not to any form of phase inhomogeneity, but this is inconsistent with the conventional rhombohedral structure of LaNiO3, and also cannot be simply explained by the common alternative orthorhombic or monoclinic distortions. ©2024 American Physical Society.
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    Observation of a charge-neutral muon-polaron complex in antiferromagnetic Cr2O3
    (American Physical Society (APS), 2019-11-26) Dehn, MH; Shenton, JK; Holenstein, S; Meier, QN; Arseneau, DJ; Cortie, DL; Hitti, B; Fang, ACY; MacFarlane, WA; McFadden, RML; Morris, GD; Salman, Z; Luetkens, H; Spaldin, NA; Fechner, M; Kiefl, RF
    We report a comprehensive muon spin rotation (μSR) study of the prototypical magnetoelectric antiferromagnet Cr2O3. We find the positively charged muon (μ+) occupies several distinct interstitial sites and displays a rich dynamic behavior involving local hopping, thermally activated site transitions, and the formation of a charge-neutral complex composed of a muon and an electron polaron. The discovery of such a complex has implications for the interpretation of μSR spectra in a wide range of magnetic oxides and opens a route to study the dopant characteristics of interstitial hydrogen impurities in such materials. We address implications arising from implanting a μ+ into a linear magnetoelectric and discuss the challenges of observing a local magnetoelectric effect generated by the charge of the muon. © Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license.
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    Spin depolarization of Muonium in Mesoporous Silica
    (IOP Publishing, 2014-12-16) Dehn, MH; Arseneau, DJ; Bridges, MD; Buck, T; Cortie, DL; Cottrell, SP; Fleming, DG; Kelly, JA; MacFarlane, WA; MacLachlan, MJ; Morris, GD; McKenzie, I; Xiao, J; Kiefl, RF
    We report muon spin rotation/relaxation measurements of muonium in mesoporous silica (SBA-15) with a high specific surface area of 600 m2/g. Up to 70 percent of the incoming muons form muonium and escape efficiently into the open pores at all temperatures between 3 and 300K. We present evidence that the interaction with the silica surfaces involves both spin exchange and a transition to a diamagnetic state, possibly due to dangling bonds on the surface. At very low temperatures, below 20K, the interaction between muonium and the silica surfaces is suppressed due to a He film coating the surfaces. These results indicate that it should be possible to use muonium to probe the surfaces of uncapped nanoparticles supported in silica. © 2014 The Authors - Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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    β-NMR of 8Li+ in rutile TiO2
    (IOP Publishing, 2014-12-16) McFadden, RML; Cortie, DL; Arseneau, DJ; Buck, TJ; Chen, CC; Dehn, MH; Dunsiger, SR; Kiefl, RF; Levy, CDP; Li, C; Morris, GD; Pearson, MR; Samuelis, D; Xiao, J; Maier, J; MacFarlane, WA
    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. © The Authors CC-BY 3.0