The Effects of La Doping on the Crystal Structure and Magnetic Properties of Ni₂In-Type MnCoGe_1-xLa_x (x = 0, 0.01, 0.03) Alloys

In this experiment, a series of MnCoGe_1-xLa_x (x = 0, 0.01, 0.03) alloy samples were prepared using a vacuum arc melting method. The crystal structure and magnetic properties of alloys were investigated using X-ray diffraction (XRD), Rietveld method, physical property measurement system (PPMS), and vibrating sample magnetometer (VSM) analyses. The results show that all samples were of high-temperature Ni₂In-type phases, belonging to space group P6₃/mmc (194) after 1373 K annealing. The results of Rietveld refinement revealed that the lattice constant and the volume of MnCoGe_1-xLa_x increased along with the values of La constants. The magnetic measurement results show that the Curie temperatures (T_C) of the MnCoGe_1-xLa_x series alloys were 294, 281, and 278 K, respectively. The maximum magnetic entropy changes at 1.5T were 1.64, 1.53, and 1.56 J·kg^-1·K^-1, respectively. The respective refrigeration capacities (RC) were 60.68, 59.28, and 57.72J·kg^-1, with a slight decrease along the series. The experimental results show that the doping of La results in decreased T_C, basically unchanged magnetic entropy, and slightly decreased RC.