Dielectric and Magnetic Properties of the Distorted Triangular Lattice Ising-Like Antiferromagnet TlCoCl₃

Abstract

Successive structural phase transitions with ferroelectricity were found in TlCoCl₃ through dielectric constant measurements and D–E hysteresis loop observations. The sequence of the transitions is identical with that in RbMnBr₃ and TlFeCl₃, which undergo successive transitions from the prototype crystal structure of CsNiCl₃. The temperature dependence of the magnetic susceptibility below T_N1 indicates the presence of successive magnetic orderings, which has not been observed in the Ising-like antiferromagnets CsCoCl₃ and CsCoBr₃ without structural transitions. Dielectric dispersion attributable to the Ising-spin dynamics on a linear-chain spin system was observed at low temperatures. Several problems to be solved are proposed for understanding structural and magnetic properties of TlCoCl₃.