Critical Behavior of CsVBr_3 and RbVBr_3

概要

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The magnetic phase diagrams of planar antiferromagnets CsVBr_3 and RbVBr_3 have been investigated by susceptibility measurements with the external field applied in the c-plane. CsVBr_3 with the CsNiCl_3 structure shows tetracritical behavior (T_N=20.3 K)as observed in CsMnBr_3. The interval of the intermediate phase is only 〜1 K at H≈8T because of the strong intrachain exchange coupling. RbVBr_3 with a chemical unit cell enlarged to√<3>a, √<3>a, c undergoes two transitions at T_<N1>=28.1K and T_<N2>=21.0K in zero field due to the inequality of exchange interactions in the c-plane. Both phase boundaries near the zero field transition points (T_0) are described as H_2∝|T-T_0|^φ with a single exponent φ≈0.8 for CsVBr_3 and φ≈1.0 for RbVBr_3. The crossover exponent φ for CsVBr_3 is smaller than the value φ≈1.04 predicted for the n=2 chiral universality class.
社団法人日本物理学会の論文
1994-08-15