Kohn-Sham density-functional approach to dense magnetic polarons in magnetic semiconductors

Using the Kohn-Sham density functional approach, we have reinvestigated the crystallization of dense magnetic polarons in antiferromagnetic semiconductors, studied earlier by the present author in the adiabatic region where the motion of localized spins is too slow to follow the translational motion of electrons [Phys. Rev. B 36, 574 (1987)]. The aim of the present paper is verification of the previous results obtained by the gradient-expansion method for an inhomogeneous electron gas. The present study gives qualitatively improved solutions and confirms the overall features revealed by the previous study: the existence of dense magnetic polarons or dense bubbles caused by the instability of the homogeneous state due to the interaction between electrons and localized spins, their characteristics, mutual transitions, etc. The only modification is that in the crystallization of dense magnetic polarons or dense bubbles, only one electron is contained in the unit cell for the case of a nondegenerate original conduction band. The importance of the treatment for the electron-electron interaction as a whole also becomes evident. Furthermore an evolution of the self-trapped magnetic polaron state, from the single self-trapped magnetic polaron to the homogeneous state, as the electron concentration increases is studied in the adiabatic region.