Importance of in-plane anisotropy in the quasi-two-dimensional antiferromagnet BaNi2V2O8.
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 c. At micro(o)H* approximately 1.5 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.
Knafo
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Forschungszentrum Karlsruhe, Institut für Festkörperphysik, D-76021 Karlsruhe, Germany.
Meingast
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C
Grube
K
K
Drobnik
S
S
Popovich
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P
Schweiss
P
P
Adelmann
P
P
Wolf
Th
T
V Löhneysen
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H