Spin nematics and magnetization plateau transition in anisotropic kagome magnets

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)similar to J and ferromagnetic J(perpendicular to)similar to J(2)/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(perpendicular to) phase diagram.