Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 54: Correlated Electrons: Complex Oxides and Other Materials

TT 54.12: Vortrag

Donnerstag, 4. April 2019, 12:30–12:45, H22

Magnetic order and short-range correlations in γ_II-Li₂FeSiO₄ — •Martin Jonak¹, Christoph Neef¹, Waldemar Hergett¹, Sven Spachmann¹, Mahmoud Abdel-Hafiez^1,2, Johannes Werner¹, Changhyun Koo¹, Sven Sauerland¹, Clemens Ritter³, Sergei Zvyagin⁴, Alexey Ponomaryov⁴, and Rüdiger Klingeler¹ — ¹Kirchhoff Institute of Physics, Heidelberg University, Heidelberg, Germany — ²Physikalisches Institut, Goethe-Universität, Frankfurt am Main, Germany — ³Institut Laue-Langevin, Grenoble, France — ⁴Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

Multi-faceted magnetic characterisation of γ_II-Li₂FeSiO₄ single crystals (space group Pmnb) is presented. The system exhibits tetrahedrally coordinated Fe²⁺ ions in a high-spin e_g³t_2g³ (i.e., S=2) configuration. While static magnetic susceptibility shows a maximum at T≈28 K, long-range AFM order is found to evolve at T_N=17.0(5) K. Elastic neutron scattering on a powder sample reveals commensurate two-sublattice AFM order with a propagation vector (1/2, 0, 1/2). At T=4 K, high-frequency electron-spin resonance (HF ESR) observes zero-field splitting of Δ = 700(20) GHz, and the closing of the AFM gap at B = 16.2(2) T which is separated from a spin-flop-like phase emerging at B = 18.0(5) T. Both transitions are confirmed by pulsed-field magnetisation. At high temperatures, magnetic anisotropy beyond the g-factor anisotropy extends up to T 150 K. The presence of short-range magnetic correlations at least up to T ≈ 110 K is detected by specific heat and magnetostriction, as well as by HF ESR.