XY-like Incommensurate Magnetic Order in Ce$_2$SnS$_5$

Abstract

We report the synthesis of single crystals of Ce$_2$SnS$_5$ through a two-stage chemical vapor transport method. The Ce$_2$SnS$_5$ system is a member of the orthorhombic $Pbam$ (No. 55) space group and realizes a distorted trigonal tricapped prism (TTP) crystal field around each cerium site. We characterized the sample through orientation-dependent magnetization and heat capacity measurements to probe the magnetic anisotropy in the system characteristic of XY-like anisotropic Heisenberg model behavior. Ce$_2$SnS$_5$ furthermore enters a zero-field ordered phase under $T_N =$ 2.4 K; powder neutron diffraction measurements reveal incommensurate magnetic order near $T_N$. The system then locks into a commensurate, two-$q$ magnetic structure below approximately 1.2 K. This commensurate structure belongs to the Shubnikov group $Pb'a'm'$ (MSG 55.359) and realizes the propagation vectors $\vec{q} = (1/3,0,0)$ and $\vec{q} = (0,0,0)$.