Low-temperature hall effect and martensitic transition temperatures in magnetocaloric Ni50Mn35Sb15-xGex (x=0, 1, 3) alloys

The field dependence of Hall resistivity rho(H) and magnetization M of the magnetocaloric Ni50Mn35Sb15-xGex (x = 0, 1, 3) alloys were measured at T = 4.2 K and in magnetic fields of up to 70 kOe. The martensitic transitions temperatures, i.e., the martensite start temperature M-S, martensite finish temperature M-F, austenite start A(S) and austenite finish A(F) temperatures, were obtained from the magnetization temperature dependence that measured from 4.2 to 350 K in a field of 1 kOe. It was observed that the martensitic transitions temperatures correlate strongly both with the valence electron concentration e/a and with the electronic transport characteristics, which are the coefficients of normal R-0 and anomalous R-S Hall effect and the concentration of charge carriers n. Apparently, similar correlations should be observed in other magnetocaloric compounds that could be used to study martensitic transitions.