Structural, Magnetocaloric, and Magnetic Properties in Heusler Ni₅₀Mn₃₅In₁₀X₅ (X = Ga, Fe and Al) Alloys

Abstract

The structural, magnetocaloric, and magnetic characteristics in Heusler Ni50Mn35In10X5 (X = Ga, Fe, and Al) alloys were examined using X-ray diffraction and field-dependent magnetization measurements. All samples exhibited a mixture structure of cubic L21 and tetragonal L10 and underwent second-order magnetic transitions at TC(Al5) = 220 K, TC(Ga5) = 252 K, and TC(Fe5) = 298 K. The Ga5 alloy exhibited structural change as indicated by a thermal hysteresis that may be seen in the saturation magnetic field in the M(T) dependences. The transition at the TC point from a ferromagnetic to a paramagnetic state caused a drop in magnetization, supported by thermal hysteresis, at a low magnetic field (0.01 T). On the other hand, the Fe5 alloy presented a gradual decrease in magnetization with similar hysteresis behavior, also at a low magnetic field (0.01 T), whereas at 0.1 T of field, no features characteristic of this transition were detected. This could be due to a large difference in the metallic radius of Fe compared to that of In. Otherwise, magnetic investigations demonstrated that the replacement of In with Al may cause the structural transformation temperatures and TC to be shifted to low temperatures. The present results imply that the structural transformation temperatures and the transition itself are highly dependent on chemical composition. Furthermore, under a magnetic field change of 5 T, the maximum magnetic entropy changes of 0.6 J/kg K, 1.4 J/kg K, and 2.71 J/kg K for the Ga5, Fe5, and Al5 alloys, respectively, were determined by their TC. Refrigeration capacity values were found to be 25 J/kg, 74 J/kg, and 98 J/kg at µ0∆H = 5 T. These ribbons are viable candidates for multifunctional applications due to their cheaper cost and their physical characteristics disclosed during the magnetostructural transition, which takes place close to the room temperature.

Keywords

• Heusler alloys
• magnetic transition
• magnetocaloric effect
• magnetic refrigerant materials