Browsing by Author "Stock, C"

Now showing 1 - 2 of 2
  • 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.
  • No Thumbnail Available
    Item
    Magnetic field splitting of the spin resonance in CeCoIn5
    (American Physical Society, 2012-10-17) Stock, C; Broholm, C; Zhao, Y; Demmel, F; Kang, HJ; Rule, KC; Petrovic, C
    Neutron scattering in strong magnetic fields is used to show the spin resonance in superconducting CeCoIn(5) (T(c) = 2.3 K) is a doublet. The underdamped resonance ((h) over bar Gamma = 0.069 +/- 0.019 meV) Zeeman splits into two modes at E(+/-) = (h) over bar Omega(0) +/- mu(B mu 0)H with alpha = 0.96 +/- 0: 05. A linear extrapolation of the lower peak reaches zero energy at 11.2 +/- 0.5 T, near the critical field for the incommensurate "Q phase." Kenzelmann et al. [Science 321, 1652 (2008)] This, taken with the integrated weight and polarization of the low-energy mode (E(-)), indicates that the Q phase can be interpreted as a Bose condensate of spin excitons. © 2012, American Physical Society.