ABSTRACT
The structural and magnetic transitions of Ni50Mn34×16 (X = Sn, Sb, and In) Heusler alloys have been investigated by thermomagnetic M(T) measurements through heating/cooling cycles. These alloys undergo structural transition from an austenite phase to a martensite phase in the temperature regime around 200 K. The martensitic transformation spans a wide temperature range (78–180 K), with thermal hysteresis characteristics of a first-order nature. In the structural transition regime, Ni50Mn34In16 shows a signature of field-induced transition from a martensite to austenite phase. At room temperature all of the alloys show a ferromagnetic austenite phase. Direct and inverse magnetocaloric properties and refrigeration capacity (RC) in these alloys were evaluated for a maximum field change of 15 kOe. In substitution reveals the largest ΔSm value of 3.0 J kg−1 K−1 at the martensitic (132 K) transition and −2.5 J kg−1 K−1 at the magnetic (316 K) transition. The magnitudes of the conventional magnetocaloric effect associated with the magnetic transition were quite comparable in all three alloys.
Acknowledgments
This work was supported by the Spanish Ministry of Science and Innovation and EU FEDER (Project MAT 2010-20537), the PAI of the Regional Government of Andalucía (Project P10-FQM-6462), and the United States Office of Naval Research (Project N00014-11-1-0311).