Andrew Boothroyd

Abstract:

Neutron time-of-flight spectroscopy has been employed to study the crystal-field splitting of Pr3+ in the pyrochlore stannate Pr 2Sn2O7. The crystal field has been parameterized from a profile fit to the observed neutron spectrum. The single-ion ground state is a well-isolated non-Kramers doublet of Γ3+ symmetry with a large Ising-like anisotropy, χzz/ χ⊥≈60 at 10 K, but with a significant admixture of terms |MJ≠±J, which can give rise to quantum zero-point fluctuations. This magnetic state satisfies the requirements for quantum spin-ice behavior. © 2013 American Physical Society.

Abstract:

Magnetic fluctuations in the molecular-intercalated FeSe superconductor Lix(ND2)y(ND3)1-yFe2Se2 (Tc=43K) have been measured by inelastic neutron scattering from a powder sample. The strongest magnetic scattering is observed at a wave vector Q≈1.4 Å-1, which is not consistent with the (π,0) nesting wave vector that characterizes magnetic fluctuations in several other iron-based superconductors but is close to the (π,π/2) position found for AxFe2-ySe2 systems. At the energies probed (∼5kBTc), the magnetic scattering increases in intensity with decreasing temperature below Tc, consistent with the superconductivity-induced magnetic resonance found in other iron-based superconductors. © 2013 American Physical Society.