Design of thermal hysteresis in nonstoichiometric alloys with giant magnetocaloric effect

Abstract

The non-stoichiometric Fe${}_2$P-type (FeMnP${}_{0.5}$Si${}_{0.5}$)${}_{1-x}$(FeV)${}_x$ alloys ( $x=0,0.01$, $0.02$, and $0.03$) have been investigated as potential candidates for magnetic refrigeration near room temperature. The magnetic ordering temperature decreases with increasing FeV concentration, $x$, which can be ascribed to decreased ferromagnetic coupling strength between the magnetic atoms. The strong magnetoelastic coupling in these alloys results in large values of the isothermal entropy change ($\Delta S_M$); $15.7$ J/kgK, at $2$ T magnetic field for the $x=0$ alloy. $\Delta S_M$ decreases with increasing $x$. Results from M{ö}ssbauer spectroscopy reveal that the average hyperfine field (in the ferromagnetic state) and average center shift (in the paramagnetic state) have the same decreasing trend as $\Delta S_M$. The thermal hysteresis ($\Delta T_{hyst}$) of the magnetic phase transition decreases with increasing $x$, while the mechanical stability of the alloys improves due to the reduced lattice volume change across the magnetoelastic phase transition. The adiabatic temperature change $\Delta T_{ad}$, which highly depends on $\Delta T_{hyst}$, is $1.7$ K at $1.9$ T applied field for the $x=0.02$ alloy.

References in corpus (3)

• Mixed Magnetism for Refrigeration and Energy Conversion
• Site-specific atomic substitution in a giant magnetocaloric Fe${}_2$P-type system
• A setup for direct measurement of the adiabatic temperature change in magnetocaloric materials