In the past 20 years, there has been a surge in research on the magnetocaloric response of materials, due mainly to the possibility of applying this effect for magnetic refrigeration close to room temperature. This review is devoted to the main families of materials suitable for this application and to the procedures proposed to predict their response. Apart from the possible technological applications, we also discuss the use of magnetocaloric characterization to gain fundamental insight into the nature of the underlying phase transition.

The temperature dependent electrical and thermal properties including electrical resistivity (q), specific heat (C P), Seebeck coefficient (S) and thermal conductivity (j) have been studied for the polycrystalline NiTi, Ti 50 Ni 40 Cu 10 and Ti 50 Ni 48.5 Fe 1.5 shape memory alloys from 10-400 K. It was found that the electrical resistivity and Seebeck coefficient exhibit a typical metallic behavior throughout the temperature range investigated. A significant thermal hysteresis between warming and cooling was observed in all the three alloys which is a manifestation of the first-order nature of martensitic transitions. Our results indicate the presence of two stage martnesite transformations, i.e. B2 ! B19 ! B19 0 for Ti 50 Ni 40 Cu 10 while B2 ! R ! B19 0 for NiTi and Ti 50 Ni 48.5 Fe 1.5 alloys. An analysis on the measured thermal conductivity reveals that the anomalous feature in j at the B19 $ B19 0 transformation for Ti 50 Ni 40 Cu 10 is essentially attributed to the electronic contribution, while an enormously large peak in warming run observed at the B19 ! B2 transformation is due to the change in lattice thermal conductivity. V

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First order structural transformation (FOST) and inverse magnetocaloric effect (IMCE) were investigated in melt-spun ribbons of Ni49Mn37.4Sn13.6 and Ni50Mn34.5Sn15.5 Heusler alloys. Thermal and magnetic characterization of the ribbons revealed the existence of FOST. Interestingly, in the Ni49Mn37.4Sn13.6 ribbon, the structural transformation occurs prior to magnetic transition incongruous to that observed in the Ni50Mn34.5Sn15.5 ribbons. In addition to FOST, the ribbons also exhibit a large IMCE at low magnetic field. A maximum positive magnetic entropy change ΔS M ∼ 6.0 J kg−1 K−1 and ∼1.6 J kg−1 K−1 for a field change of 2 T was observed in the Ni49Mn37.4Sn13.6 and Ni50Mn34.5Sn15.5 ribbons, respectively.