Abstract
As a typical two-dimensional frustrated quantum magnet,the triangular-lattice antiferromagnet exhibits a series of exotic states from the complicated interplay of the lattice,spin,electron,and orbit with quantum and thermal fluctuations.From the ground state of a triangular-lattice Heisenberg antiferromagnet with coplanar 120° ordering,a series of magnetization anomalies can manifest under a magnetic field,such as the 1/3 magnetization plateau(Ms/3)and umbrella-shaped phase.This Ms/3 plateau state is recognized as an up-up-down structure stabilized by the quantum effect.By surveying theoretical research and experimental measurements on triangular-lattice antiferromagnets,this review article describes the current understanding of the magnetic properties of triple-perovskite antiferromagnets A3MB2O9(A=Ba,Ca,and Sr;M=Co,Ni,and Mn;B=Sb,Nb).Through examining both the bulk properties and spin dynamics,fascinating insights into the quantum effect on the triangular lattice are discussed.