Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 47: Frustrated Magnets - Iridates and Fe-based Materials

TT 47.12: Talk

Wednesday, March 14, 2018, 12:30–12:45, H 0104

Role of single-ion anisotropy in Fe³⁺-based frustrated magnets — •Alexander A. Tsirlin — EP VI, EKM, University of Augsburg, Germany

Transition-metal ions with the half-filled d-shell and the high-spin d⁵ electronic configuration are magnetically nearly isotropic. Here, using density-functional calculations juxtaposed with the experimental data from thermodynamic measurements and neutron diffraction, I will argue that such d⁵ ions still feature a non-negligible single-ion anisotropy that prevails over intersite anisotropy terms and drives multiple magnetic transitions in frustrated magnets based on Fe³⁺. The talk will cover Fe-based pyroxene compounds, where frustrated interchain interactions trigger a collinear spin-density-wave phase separating the ground-state helical order from the paramagnetic state. I will further report the sequence of magnetic transitions in the Cairo antiferromagnet Bi₄Fe₅O₁₃F, where competing single-ion anisotropies introduce two flavors of orthogonal order separated by a collinear phase. Despite their small size, typically less than 1% of the isotropic exchange couplings, the single-ion terms play pivotal role for the magnetically ordered states of Fe³⁺ compounds.