Direct and inverse magnetocaloric effect in Ni1.81Mn1.64In0.55, Ni1.73Mn1.80In0.47, and Ni1.72Mn1.51In0.49Co0.28 Heusler alloys

Resumo

The magnetic and magnetocaloric properties of Ni_1.81Mn_1.64In_0.55, Ni_1.73Mn_1.80In_0.47, and Ni_1.72Mn_1.51In_0.49Co_0.28 Heusler alloys are investigated. The magnetocaloric effect (MCE) is experimentally measured using the direct method with the help of different protocols. The phase transformation temperatures and the latent heat of metamagnetostructural transitions are determined from the temperature dependences of magnetization and via differential scanning calorimetry. In the case of Ni_1.81Mn_1.64In_0.55 and Ni_1.73Mn_1.80In_0.47 alloys, the temperature shift of martensitic transformation induced by external magnetic field is found. It is demonstrated that, in the Ni_1.72Mn_1.51In_0.49Co_0.28 alloy, added Co atoms raise the temperature of structural and magnetic phase changes and enhance the MCE. In addition, it is revealed that the MCE depends on measurement protocols near the first-order phase transition.