Abstract
The magnetization and the magnetocaloric effect of eight Ni-Mn alloys containing 66-83 at%Ni have been investigated in connection with Ni content.
In those alloys annealed for a relatively short time, the measurements were made in the temperature range extending over some hundred degrees above and below room temperature. The curves indicating the temperature-dependence of saturation magnetization in six alloys containing 71-83 at%Ni showed trends approximately similar to those of the ferromagnetic 3d transition elements. From such a trend curve it was possible to evaluate roughly the ferromagnetic Curie temperature, TF, but it was known that the precise evaluation of TF was more difficult in those alloys than in the 3d transition elements. Then, for those six alloys the values of spontaneous magnetization in the temperature range near TF were derived from the experimental results of the magnetocaloric effect, and the values of TF were determined.
The curves showing the relation between the relative spontaneous magnetization and the reduced temperature, derived from the above-mentioned results for those six alloys, almost agreed with each other. Consequently, the law of corresponding states holds for those alloys. In addition, the curve indicating this law fits on the whole the theoretical curve derived from the Brillouin function whose total angular momentum quantum number is 5/2. On the basis of the results described above, the values of the coefficient of Weiss molecular field at TF and the strength of molecular field at 0 K were calculated for those six alloys. It was also shown that those values varied systematically with increasing Ni content.
