Spin nematics and magnetization plateau transition in anisotropic kagome magnets

Abstract

We study S=1 kagome antiferromagnets with an isotropic Heisenberg exchange J and strong easy-axis single-ion anisotropy D. For D≫J, the low-energy physics can be described by an effective S=1/2 XXZ model with antiferromagnetic J_z∼J and ferromagnetic J_⊥∼J²/D. Exploiting this connection, we argue that nontrivial ordering into a “spin-nematic” occurs whenever D dominates over J, and discuss its experimental signatures. We also study a magnetic field induced transition to a magnetization plateau state at magnetization 1/3 which breaks lattice translation symmetry due to ordering of the S^z and occupies a lobe in the B/J_z−J_z/J_⊥ phase diagram.