The magnetic and structural phase diagram of the Heusler-series (Co1−xNix)2NbSn

Abstract We present a study of the magnetic and structural phase transitions of the pseudo-ternary Heusler series (Co1−xNix)2NbSn. Co2NbSn undergoes a structural transition at T S =233 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. Upon alloying Co2NbSn with Ni, both the structural and the magnetic phase transition temperatures are suppressed with Ni content x to zero temperature at x=0.32 (TC) and 0.47 (TS). These observations disprove previous reports. We discuss the implications of our findings for the band structure of this material class.