On correctly assessing the reversibility of the magnetocaloric effect from indirect measurements

Abstract

The adiabatic temperature change ($\Delta T_{ad}$) of a magnetic refrigerant can be indirectly estimated through field ($H$) and temperature ($T$) dependent magnetization ($M$) and specific heat ($C_p$) measurements. A direct integration approach for this estimation is frequently reported, which is an approximation to a rigorous mathematical approach. In this work, we propose an iterative method in small $H$ steps, to estimate $\Delta T_{ad}$ from indirect measurements. We show that this approach is able to reproduce the reversibility of the magnetocaloric effect, and provides a more accurate estimation of $\Delta T_{ad}$, up to 10\% when considering a detailed $M(H,T)$ and $Cp(H,T)$ dataset that reproduces the magnetothermal properties of gadolinium, a benchmark room-temperature magnetic refrigerant.