The effect of Co doping on the magnetic entropy changes in Ni44−xCoxMn45Sn11 alloys

A series of Ni44−xCoxMn45Sn11 (x = 0, 1, and 2) ferromagnetic shape memory alloys (FSMAs) were prepared by arc melting method. The martensitic transition (MT) and Curie temperatures vary obviously with Co addition. With the increasing temperature, the magnetization increases from a weak-magnetic martensite to a ferromagnetic austenite, for x = 0 and 1. But in the case of x = 2, the magnetization increases from a ferromagnetic martensite to another ferromagnetic austenite. Under an applied magnetic field of 10 kOe, the peak values of magnetic entropy changes are 10.1, 14.1, and 6.2 J/(kg K), for x = 0, 1, and 2, respectively. The magnetic phase transition near the martensitic transition temperatures and the field-induced metamagnetism should account for the large magnetic entropy changes.