Structure and magnetic order of the Heusler compound Co2NbSn -: art. no. 174428

We present a detailed study of the structural and magnetic phase transitions of the Heusler compound Co2NbSn. This material undergoes a structural transition at T-S=235 K from the cubic Heusler Fm3m high-temperature phase into an orthorhombic low-temperature lattice of Pmma symmetry. Further, the system exhibits a magnetic transition at T-C=116 K from para- to ferromagnetism. While on a macro- and mesoscopic scale Co2NbSn appears to be fully Fm3m ordered, from microscopic studies we find that on an atomic scale site disorder is present. We discuss the implications of these findings for the anomalous macroscopic physical properties and domain formation in the ferromagnetic state in Co2NbSn.