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TT: Fachverband Tiefe Temperaturen

TT 12: Correlated Electrons: Frustrated Magnets - General 1

TT 12.7: Vortrag

Montag, 20. März 2017, 16:45–17:00, HSZ 03

Anisotropy governed competition of magnetic phases in the honeycomb quantum magnet Na₃Ni₂SbO₆ — •Johannes Werner¹, Waldemar Hergett¹, Mario Gertig¹, Jaena Park¹, Changhyun Koo¹, and Rüdiger Klingeler^1,2 — ¹Kirchhoff Institute for Physics, Heidelberg University, Heidelberg, Germany — ²Centre for Advanced Materials, Heidelberg University, Heidelberg, Germany

Thermodynamic properties as well as low-energy magnon excitations of the layered S=1 honeycomb-lattice system Na₃Ni₂SbO₆ have been studied by high-resolution dilatometry, high-field magnetometry, and antiferromagnetic resonance (AFMR) studies in magnetic fields up to 18 T. At T_N = 16.5 K, there is a tricritical point separating two antiferromagnetic phases AF1 and AF2 from the paramagnetic regime. In the AF1 phase below B_C1≈ 9.5 T (at 4.2 K), the AFMR modes suggest a two-sublattice spin configuration which is consistent with stripe-like order. Observed zero field splitting Δ_ZFS = 360 GHz of the AFMR modes indicates an uniaxial anisotropy field B_A = 1.7 T. We conclude the crucial role of the axial anisotropy favoring the AF1 spin structure over the AF2 one. While magnetostriction data disprove a simple spin-flop scenario at B_C1, the nature of a second transition at B_C2≈ 13 T remains unclear. Both the sign of the magnetostriction dL/dB and Grüneisen scaling suggest that short-range antiferromagnetic correlations present at least up to ∼ 5· T_N are of AF2-type, i.e. the intermediate field phase.