APW Research of Europium Monochalcogenides. I. Band Structures and Electron—Electron Interaction in Ferromagnetic Semiconductors

The augmented plane wave method (APW) is used for a theoretical study of the electron properties of europium monochalcogenides. Spin‐polarized energy band calculations of the ferromagnetic EuO, EuS, and EuSe explain qualitatively the exchange interactions therein. Based on the APW data in the frame of perturbation theory the Coulomb electron—electron interaction at the 4f shell of europium is taken into account for EuO and EuS. The band structures and the multiplet terms of the f6d and 3d94f8 excited states gives a new interpretation of a known experimental spectra for these compounds.