Magnetic Susceptibilities of the Frustrated Triangular Lattice Antiferromagnets CsVCl₃ and VX₂ (X=Cl, Br and I): Appearance of Magnetic Liquid in the Ordered State

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Magnetic susceptibilities χ of the frustrated triangular lattice antiferromagnets CsVCl₃ and VX₂ (X=Cl, Br and I) have been measured by means of the conventional Faraday-type as well as the SQUID magnetometers. The χ-T curve of CsVCl₃ shows a typical 1D-like character in agreement with the early work by Niel et al. At T<T_N, χ_c increases rapidly with decreasing T, whereas χ_a stays at a constant value. The χ-T curve in VX₂ which are thought to be 2D-like systems is very flat and shows an anomaly at T_N. Surprizingly, however, no anisotropy could be detected below T_N. This suggests that the transition is quite different from the conventional one for the non-frustrated antiferromagnetic systems and a magnetic liquid state is formed in the ordered state.