Magnetic order in CeAuSn

CeAuSn is a hexagonal, rare-earth based intermetallic compound exhibiting antiferromagnetic order below T_N = 4.1 K as evidenced by anomalies in thermodynamic properties. In order to study the magnetic order using a microscopic probe, neutron diffraction was performed on a CeAuSn single crystal. Diffraction pattern were recorded using the neutron Laue diffractometer CYCLOPS at ILL. Allowing fast exploration of reciprocal space, this innovative instrument only recently became available for users. Data were taken at temperatures between T = 1.6 and 10 K. Our measurements confirm the hexagonal crystal structure at low temperatures and additional magnetic peaks are clearly visible at lowest temperatures. They can be indexed by a commensurate propagation vector k = (1/2 0 0). Moreover, the magnetic intensity vanishes at T_N ∼ 4.1 K in line with thermodynamic measurements. Although CeAuSn is an XY system on a triangular lattice where geometrical frustration might play a role, we do not find evidence for the existence of frustration.