Low hysteresis loss and moderate magnetic entropy change near room temperature in the bulk Ni39Co7Mn43Sn7Ti4 alloy

Abstract

Ni-Co-Mn-Sn alloys with a significant magnetocaloric effect are considered promising candidates for room-temperature magnetic refrigeration. Alloying serves as an effective method to tune the working temperature and magnetocaloric properties of Ni-Co-Mn-Sn alloys. Here, we report the phase transformation and magnetocaloric properties of polycrystalline Ni39Co7Mn43Sn7Ti4 by alloying with a relatively high Ti content. This alloy displays a first-order martensitic transformation (MT) near room temperature and a second-order magnetic transition in austenite at 366 K. The application of a magnetic field significantly widened the temperature range of the MT, thereby contributing to a substantial effective refrigeration capacity of 198 J kg-1 at a magnetic field change of 5 T. Moreover, the alloy exhibits simultaneously a moderate isothermal magnetic entropy change (12.2 J kg-1 K-1) and a low average hysteresis loss (40 J kg-1) due to the weakened magnetic field-induced reverse martensitic transformation caused by Ti alloying.