Magnetocaloric effect near room temperature in quintenary and sextenary Heusler alloys

Abstract

An inverse magnetocaloric effect is studied in Ni 2Mn 1 + x X 1 - x-type Heusler alloys. Principally known for their shape-memory properties, these alloys also exhibit significant entropy and temperature changes (Δ S and Δ T A d, respectively) under adiabatic conditions when a modest magnetic field is applied. We investigated the impact on magnetocaloric properties of introducing substantial chemical disorder on the X-site (X = Si, Ga, In), of replacing Ni with nonmagnetic Ag, and of replacing a small amount of Mn with Gd. While a reduction in Δ S is observed in the first two cases, we observe a significant enhancement of Δ S when a small amount of Gd is substituted for Mn. A thermodynamic analysis was conducted using magnetization and heat capacity data to estimate adiabatic temperature changes in the range of Δ T A d ≃ - 1 to - 3 K for a 5 T magnetic field. Several alloys characterized in this study exhibit these respectable Δ T A d values near room temperature, making them potentially viable candidates for magnetic refrigeration applications.