Martensitic phase transition with magnetocaloric effect and double-shifted exchange bias in the martensitic phase for Ni48Mn39Sn13-xGex alloys

Ni48Mn39Sn13-xGex (x = 1, 2) Heusler alloys have been prepared, and the martensitic phase transition (MPT), magnetocaloric effect and exchange bias (EB) have been explored. At room temperature, the structure of both samples presents L2(1) type, and the MPT shifts to a higher temperature, while the Curie temperature (T-C) of the austenitic phase decreases with the increase of the Ge content. The maximum magnetic entropy change of Ni48Mn39Sn13-xGex with x = 2 reaches about 14.67 J/kg K under the magnetic field of 5 T during reverse MPT. In addition, an interesting phenomenon is the enhancement of EB with the increase of the Ge content, especially the abnormal presence of the double-shifted hysteresis loop has been realized in Ni48Mn39Sn13-xGex with x = 2, which can be interpreted by the fact that the antiferromagnetic (AFM) regions couple with proximal ferromagnetic (FM) regions in the opposite way at low temperature.