Reverse magnetostructural transformation in Co-doped NiMnGa multifunctional alloys

We studied the composition dependence of the structural and magnetic properties of Co-doped Ni-Mn-Ga alloys around the Mn-rich composition Ni50Mn30Ga20. By varying the Co and Mn content we have been able to tune the critical temperatures. In particular, in a suitable composition range, the Curie temperature of martensite is lower than Curie temperature of austenite and lower than martensitic transformation temperature, giving rise to a paramagnetic gap between magnetically ordered martensite and austenite and to the occurrence of a reverse magnetostructural transformation.