Dielectric anomaly involving magnetic phase transition in a hexagonal antiferromagnet RbCoBr₃

Abstract

Abstract The dielectric and magnetic phase transitions in a triangular lattice antiferromagnet RbCoBr3 were studied by means of some dielectric, magnetic and calorimetric measurements. In this compound, which is a typical Ising-like antiferromagnet with antiferromagnetic moment along the hexagonal c-axis, a ferroelectric phase transition involving magnetic ordering with weak ferromagnetic moments confined in the c-plane was found to occur at T N(=37.OK). Those results imply that the magnetic ordering of this system is assisted by a polar lattice distortion, which can release partially the spin frustration due to the antiferromagnetic spin arrangement on a triangular lattice. This co-ordering is certainly ascribed to a probable competition between lattice-system and spin-system. Experimental data on this interesting phenomenon are presented and a possible mechanism is proposed.