Magnetic-Field Induced Quantum Phase Transitions in Triangular-Lattice Antiferromagnets

Abstract

Cs2 CuBr4 and Ba3 NiSb2 O9 are magnetically described as quasi-two-dimensional triangular-lattice antiferromagnets with spin-1 and 1, respectively. We show that both systems 2 exhibit a magnetization plateau at one-third of the saturation magnetization Ms due to the interplay of spin frustration and quantum fluctuation. In Cs2CuBr4 that has a spatially anisotropic triangular lattice, successive magnetic-field induced quantum phase transitions including a magnetization plateau 2 Ms were observed. For Ba3 NiSb2 O9 , we performed exact 3 diagonalization for rhombic spin clusters with up to 21-sites to analyze the magnetization process. The calculated results are in agreement with experimental observations.