Inverse magnetocaloric effect in metamagnetic In-based alloys at high magnetic fields

Magnetocaloric effects (MCE) in Ni$_{\mathrm{50}}$Mn$_{\mathrm{35}}$In$_{\mathrm{15}}$, Ni$_{\mathrm{50.2}}$Mn$_{\mathrm{34.85}}$In$_{\mathrm{14.95}}$,$_{\mathrm{\thinspace }}$and Ni$_{\mathrm{50}}$Mn$_{\mathrm{35}}$In$_{\mathrm{14.25}}$Â$_{\mathrm{0.75}}$ Heusler alloys have been studied through direct measurements of the adiabatic temperature change ($\Delta $T$_{\mathrm{ad}})$ using the extraction method for magnetic field changes up to 14 T. Both the $\Delta $T$_{\mathrm{ad}}$ and the entropy changes ($\Delta $S$_{\mathrm{M}})$ increase as the martensitic transition approaches the Curie temperature of the austenitic phase. The $\Delta $T$_{\mathrm{ad}}$ increases up to a maximum value of 15 K with field and saturates at high fields. The influence of the rate of change of the magnetic field and the rate of heating to the initial temperature before applying field on the $\Delta $T$_{\mathrm{ad}}$ of Ni$_{\mathrm{50}}$Mn$_{\mathrm{35}}$In$_{\mathrm{14.25}}$Â$_{\mathrm{0.75}}$ has been studied. It has been shown that increasing the heating rate from 6 to 22 K/min results in an increase of $\Delta $T$_{\mathrm{ad}}$ by about 40{\%} for $\Delta $H$=$10 T. Acknowledgements: This work was supported by the U.S. Department of Energy, DOE Grant No. DE-FG02-06ER46291 (SIU) and DE-FG02-13ER46946 (LSU).