Effects of different rare earths on the temperature dependence of rare earth cobalt magnets

In many applications, it is necessary to have permanent magnets whose characteristics vary little around a temperature T
r
. We have developed a calculation to describe the thermal variation of the magnetization of the rare earth (RE) in such magnets including the effects of crystalline field. The exchange field of cobalt has been deduced at all temperatures from magnetization measurements on a single crystal of YCo
5
. From the calculation we can deduce the concentration x
0
, which gives dM/dT = 0 around room temperature, the resulting magnetization and the corresponding
d^{2}M/dT^{2}
.