Hysteresis loss reduction and magnetocaloric effect improvement in the Ni-Co-Mn-In alloys

In this work the magnetocaloric effect (MCE) and hysteresis losses of Ni45Co5Mn(37-x)In(13+x) alloy (x= 0, 0.4) are studied. Also we propose a new approach in calculating the average entropy change to eliminate the overestimation of the magnetic entropy change calculation using Maxwell’s relations which is commonly seen in the indirect MCE calculation in the literature. The attributes of magnetostructural coupling have an important role in the magnetic behavior of these magnetofunctional alloys. This work exhibits that a strong magnetostructural coupling can be achieved over a wide temperature range in this alloy family which results in a higher MCE and relative cooling power (RCP) compared to other Ni-Mn-In based Heusler alloys. It’s shown that by increasing the applied field the peak of the entropy change curves shifts to lower temperatures. Additionally, a small variation in the stoichiometry composition broadens the magnetic entropy change curve and shifts the critical temperatures by about 36 K to around room temperature. Furthermore, due to the enhancement in ferromagnetic exchange interactions in austenite, the magnetization change accompanying the martensitic transformation is greatly improved, resulting in a large magnetic entropy change of 31 Jkg-1K-1 under 5T field. The broadened and higher peak of the entropy change curves produced a significantly high relative cooling power in Ni45Co5Mn36.6In13.4 (488 JKg-1) and Ni45Co5Mn37In13 (317 JKg-1) under 5T field. These results are especially promising in finding low-cost, high-performance magnetocaloric material for magnetic refrigeration systems.