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Importance of In-Plane Anisotropy in the Quasi Two-Dimensional Antiferromagnet BaNi$_{2}$V$_{2}$O$_{8}$

W. Knafo·C. Meingast·K. Grube·S. Drobnik·P. Popovich·P. Schweiss·P. Adelmann·Th. Wolf·H. V. Löhneysen
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Abstract

The phase diagram of the quasi two-dimensional antiferromagnet BaNi$_{2}$V$_{2}$O$_{8}$ is studied by specific heat, thermal expansion, magnetostriction, and magnetization for magnetic fields applied perpendicular to $\mathbf{c}$. At $μ_0H^{*}\simeq1.5$ T, a crossover to a high-field state, where $T_N(H)$ increases linearly, arises from a competition of intrinsic and field-induced in-plane anisotropies. The pressure dependences of $T_N$ and $H^{*}$ are interpreted using the picture of a pressure-induced in-plane anisotropy. Even at zero field and ambient pressure, in-plane anisotropy cannot be neglected, which implies deviations from pure Berezinskii-Kosterlitz-Thouless behavior.

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W. Knafo, C. Meingast, K. Grube, S. Drobnik, P. Popovich, P. Schweiss, P. Adelmann, Th. Wolf, H. V. Löhneysen. 2007-09-28. Importance of In-Plane Anisotropy in the Quasi Two-Dimensional Antiferromagnet BaNi$_{2}$V$_{2}$O$_{8}$. https://doi.org/10.1103/physrevlett.99.137206

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