PHASE TRANSITIONS IN A FERROMAGNETIC SEMICONDUCTOR .I.

An analysis is given of the conditions for ferromagnetic phase transitions in an idealised semiconductor model containing magnetic ions. The system is described by a constant interaction - 2 J/N between the magnetic ions (Spin I) and the electrons, by the energy gap Δ between two infinitely narrow bands and by the concentration c of the magnetic ions. We find a great variety of ferromagnetic behavior. In particular there exists the possibility for the magnetization to disappear with a first or second order transition as the temperature decreases or increases. Some magnetization curves are evaluated numerically. © 1969 Springer-Verlag.