On tuning the magnetocaloric effect in Ni-Mn-In Heusler alloy ribbons with thermal treatment

An improvement of the magnetocaloric response in Ni 50.0Mn 35.5In 14.5 Heusler alloy ribbons after annealing is reported. Furthermore, the phase of the annealed sample at room temperature can be austenite or martensite depending on the annealing conditions. Short-time thermal treatments during 10 min at temperatures of 1048 and 1073 K enhance both the maximum values of structural and magnetic entropy changes (ΔS Mpk), and the refrigerant capacity (RC) of the as-spun sample. For a magnetic field value of 3 T, an enhancement in ΔS Mpk of ∼175% and ∼40%, and in RC of ∼25% and ∼20%, have been obtained in the temperature ranges where these structural and magnetic entropy changes take place, respectively. In addition, the ΔS Mpk values have been calculated using both the Clausius-Clapeyron equation and the Maxwell relation, showing a good agreement between them in the main existing first-order phase transitionsAuthors thank to Spanish MICINN for financial support under MAT2009-13108-C02-01-02 and MAT2010-20798-C05-0