Abstract
In order to clarify structural and magnetic phase transitions of a hexagonal triangular antiferromagnet TlFeCl3, dielectric and magnetic susceptibilities, D-E hysteresis loops and optical birefringence were measured. Successive structural phase transitions at 179 K(T2), 83 K(T3) and 79 K(T4) were identified. At a range of temperatures T4 < T < T3 (phase IV), opened D-E loops were clearly observed. The dielectric behavior of the successive structural phase transitions of TlFeCl3 were confirmed to be quite similar to those of KNiCl3 and RbMnBr3 which are Group I of KNiCl3-family crystals.
