Quantum magnetic properties of the spin-1/2 triangular-lattice antiferromagnet Ba${}_2$La${}_2$CoTe${}_2$O${}_{12}$

Abstract

We report the crystal structure of Ba${}_2$La${}_2$CoTe${}_2$O${}_{12}$ determined by Rietveld analysis using X-ray powder diffraction data. It was found from magnetic measurements that Ba${}_2$La${}_2$CoTe${}_2$O${}_{12}$ can be described as a spin-1\2 triangular-lattice antiferromagnet with easy-plane anisotropy at low temperatures. This compound undergoes a magnetic phase transition at $T_{\mathrm{N}}=3.26$ K to an ordered state with the $120^{\circ }$ structure. The magnetization curve exhibits the one-third plateau characteristic of triangular-lattice quantum antiferromagnets. The antiferromagnetic exchange interaction and the $g$ factors parallel and perpendicular to the $c$ axis were evaluated to be $J/k_{\mathrm{B}}=22$ K, $g_{\parallel }=3.5$ and $g_{\perp }=4.5$, respectively.

8 pages, 7 figures, 2 tables