Theory of ferromagnetism in (A, Mn)B semiconductors

A brief review of theory of ferromagnetism of diluted magnetic semiconducto rs of the form (A, Mn) B based on the double-exchange model is first given. A systematic investigation of the phenomena extending the current theory i s outlined. We begin with an investigation or regions of instability of the non-magnetic towards the ferromagnetic state of a system of Mn atoms doped in an AB-type semiconductor. A self-consistent many-body theory of the fer romagnetic state is then developed, going beyond the mean-field approaches by including fluctuations of the Mn spins and the itinerant hole gas. A fun ctional theory suitable for computation of system properties such as the Cu rie temperature as a function or the hole and the Mn concentrations, the sp in current, etc., is formulated.