Broad first-order magnetic entropy change curve in directionally solidified polycrystalline Ni-Co-Mn-In

• Published in: Journal of alloys and compounds 2017-12, Vol.727, p.603-609
• Main Authors: Chen, F., Tong, Y.X., Li, L., Sánchez Llamazares, J.L., Sánchez-Valdés, C.F., Müllner, P.
• Format: Article
• Language: English
• Subjects: Bridgman method; Broad martensitic transformation; Chemical elements; Directional solidification; Entropy; Ferromagnetic shape memory alloy; Magnetocaloric properties; Manganese; Martensitic transformations; Ni-Co-Mn-In; Polycrystals; Studies; Working temperature range
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.08.118

We present the thermal dependence of the magnetic entropy change ΔSM(T) across the martensitic transformation for a polycrystalline sample, which was cut from a directionally solidified rod, with a nominal composition Ni42Co8Mn38In12 grown by the Bridgman-Stockbarger technique. This material combines a first-order martensitic transformation expanded over a very large working temperature range with a large magnetization change of ∼86 A m2 kg−1. Accordingly, for a magnetic field change of 5 T (2 T), the coupled magneto-structural transition gives rise to a broad magnetic entropy change curve across the reverse martensitic transformation with a moderate maximum value of 6.8 (3.0) J kg−1 K−1 and a full-width at half-maximum δTFWHM for the ΔSM(T) curve of 49 (43) K. Such a broad structural transition may be due to the effect of chemical segregation introduced by the directional solidification which can be enhanced by the non-uniform distribution of second phase particles. Accompanying with such a wide working temperature range, a large refrigerant capacity of 334 J kg−1 was obtained for a field change of 5 T. •Chemical heterogeneity is enhanced by decomposition via precipitation.•The working temperature range is extended to 49 K.•A large value of refrigerant capacity (334 J kg−1) is achieved.