  In this pedagogical paper, the comparative analysis of two common approaches
describing the ferromagnetic phase transition in diluted magnetic
semiconductors (DMS) is expounded in terms of Weiss field approximation.
Assuming a finite spin polarization of the magnetic ions, the treatment of
carrier-ion exchange interaction in first order evokes the homogeneous Weiss
molecular field that polarizes the spins of free carriers. In turn, this spin
polarization of the free carriers exerts the effective field that may stabilize
DMS spin polarization below a critical temperature Tc. The treatment of such
self-consistent spontaneous DMS magnetization can be done in terms of spin-spin
interaction independent on inter-ion distance and infinitesimal in
thermodynamic limit. On the other hand, the taking additionally into account
the second order effects of carrier-ion exchange interaction treat a Weiss
field in term of the RKKY indirect spin-spin interaction, which oscillates and
not disappears at finite inter-ion distance in case of finite carriers
concentration. These both approaches result in same Curie temperature Tc
provided non-correlated homogeneous random distribution of the localized spin
moments over sample volume. We discuss the origin of such coincidence and show
when this is not a case in other more realistic models of the conducting DMSs.
