Magnetocaloric Effect in Ga-Free Ni₅₀Mn₃₄×₁₆ (X = In, Sn, and Sb) Heusler Alloys

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 ΔS_m 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.

KEYWORDS:

• Heusler alloys
• magnetocaloric
• martensite
• austenite
• magnetic entropy change

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).