Temperature Dependence of the Magnetization in Ferrimagnets

Below the Curie temperature of a collinear ferrimagnet, there is a spontaneous magnetization, just as in the ferromagnets. However, in this case the magnetization is the vector sum of the magnetizations of the two antiparallel sublatticcs and therefore has the magnitude 

Case I. Tc 0 so that the material is always paramagnetic If TCJ as given by equation 108, is set equal to zero, the boundary line a( = 1 is found for the boundary of this region in the a-p plane. 

From this it follows that M (0) M0i in region USB, M (0) M02 in region USA. 

At a temperature slightly below Tc a combination of equations 115, 116, and 117 gives 

From equation 119 it follows that Ms changes sign along the line defined by 

---