Ni-Mn based conventional full Heusler alloys, all-d-metal full Heusler alloys, and their promising functional properties to solid state cooling by magnetocaloric effect

Ni-Mn based full Heusler alloys have attracted a lot of attention to utilize their promising solid-state cooling effects because of their giant magnetocaloric effects (MCEs) resulting from a first-order magnetostructural martensitic phase transformation. However, a large thermal hysteresis as well as intrinsic brittleness in conventional full Heusler alloys must be overcome to be applicable for magnetic cooling devices. All-d-metal full Heusler alloys have been recently suggested to suppress a strong covalent p-d orbital hybridization which should be attributed to poor mechanical properties and replace it with a relatively weak d-d hybridization, leading to large MCEs as well as significantly enhanced mechanical properties, especially ductility. In the review, we discuss the crystal structure, martensitic transformation, magnetic ground states, the p-d and d-d hybridization, and MCEs of both conventional and all-d-metal Ni2MnZ full Heusler alloys. Also, we suggest some perspectives to be investigated for practical application.