Influence of Cr substitution on the reversibility of the magnetocaloric effect in Ni-Cr-Mn-In Heusler alloys

We present the effect of substitution-induced pressure on the reversibility of the magnetocaloric effect (MCE) in ${\mathrm{Ni}}_{2}{\mathrm{Cr}}_{x}{\mathrm{Mn}}_{1.4\ensuremath{-}x}{\mathrm{In}}_{0.6}$ ($x=0.1$, 0.2, 0.3) alloys, through characterization in pulsed magnetic fields. We measured the adiabatic temperature change $\mathrm{\ensuremath{\Delta}}{T}_{\text{ad}}$ directly during applied magnetic field pulses of 2 and 6 T. We paid special attention to the reversibility of $\mathrm{\ensuremath{\Delta}}{T}_{\text{ad}}$. The substitution of Mn by Cr in ${\mathrm{Ni}}_{2}{\mathrm{Mn}}_{1.4}{\mathrm{In}}_{0.6}$ leads to a negative pressure, as evidence by the increase of the lattice parameters, which shifts the martensitic transition towards lower temperatures and enhances the ferromagnetism of the martensite phase. We found a large value of $\mathrm{\ensuremath{\Delta}}{T}_{\text{ad}}=\ensuremath{-}7$ K at $T=270$ K for the sample with $x=0.1$ for a field change of 6 T. We discuss the reversibility of the MCE in these alloys in terms of the Clausius-Clapeyron equation.