Browsing by Author "Dunsiger, SR"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Coupled short-range ferroelectric and magnetic order in PbFe1/2Nb1/2O3
    (American Physical Society, 2013-09-13) Stock, C; Dunsiger, SR; Mole, RA; Li, XB; Luo, H
    A neutron scattering investigation of the magnetoelectric coupling in PbFe1/2Nb1/2O3 has been undertaken. Ferroelectric order occurs below 400 K, as evidenced by the softening with temperature and subsequent recovery of the zone center transverse optic phonon mode energy ((h) over bar Omega(0)). Over the same temperature range, magnetic correlations become resolution limited on a terahertz energy scale. In contrast to the behavior of nonmagnetic disordered ferroelectrics [namely Pb(Mg, Zn)(1/3)Nb2/3O3], we report the observation of a strong deviation from linearity in the temperature dependence of ((h) over bar Omega(0))(2). This deviation is compensated by a corresponding change in the energy scale of the magnetic excitations, as probed through the first moment of the inelastic response. The coupling between the short-range ferroelectric and antiferromagnetic correlations is consistent with calculations showing that the ferroelectricity is driven by the displacement of the body-centered iron site, illustrating the multiferroic nature of magnetic-lead-based relaxors in the dynamical regime. © 2013, American Physical Society.
  • Thumbnail Image
    Item
    Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted β-emitter 8Li
    (AIP Publishing, 2023-10-28) McFadden, RML; Asaduzzaman, M; Buck, TJ; Cortie, DL; Dehn, MH; Dunsiger, SR; Kiefl, RF; Laxdal, RE; Levy, CDP; MacFarlane, WA; Morris, GD; Pearson, MR; Thoeng, E; Junginger, T
    We report measurements of the Meissner screening profile in a Nb(300 nm)/Al2O3 thin film using 8Liβ-detected nuclear magnetic resonance (β-NMR). The NMR probe 8Li was ion-implanted into the Nb film at energies ≤ 20 keV, corresponding to mean stopping depths comparable to Nb’s magnetic penetration depth λ. 8Li’s strong dipole–dipole coupling with the host 93Nb nuclei provided a “cross-relaxation” channel that dominated in low magnetic fields, which conferred indirect sensitivity to the local magnetic field via the spin-lattice relaxation (SLR) rate 1/T1. From a fit of the 1/T1 data to a model accounting for its dependence on temperature, magnetic field, and 8Li+ implantation energy, we obtained a magnetic penetration depth λ0= 51.5(22) nm, consistent with a relatively short carrier mean-free-path ℓ= 18.7(29) nm typical of similarly prepared Nb films. The results presented here constitute an important step toward using 8Liβ-NMR to characterize bulk Nb samples with engineered surfaces, which are often used in the fabrication of particle accelerators. © © 2023 Author(s). Published under an exclusive license by AIP Publishing.
  • Thumbnail Image
    Item
    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