Magnetocaloric Properties and Magnetic Anisotropy by Tailoring Phase Transitions in NiMnGa Alloys

The giant magnetocaloric properties of NiMnGa alloys can be enhanced by suitable composition changes that make structural and magnetic transition temperatures to coincide. In this paper we report results on critical temperatures, magnetic anisotropy, and magnetocaloric effect in Ni- and Mn-rich alloys as a function of composition. A phenomenological phase diagram, useful for the identification by thermomagnetic analysis of magnetic and structural transitions in the vicinity of their coincidence, is proposed. Particular emphasis is given to the discussion of giant magnetocaloric effect of those alloys showing a first order magnetostructural transition, the method of its determination, and the potentialities for applications in the field of magnetic refrigeration. © 2008 Trans Tech Publications.