Exchange integrals in Mn- and Co-doped II-VI semiconductors

Article

关键词: DILUTED MAGNETIC SEMICONDUCTORS;    TRANSITION-METAL IMPURITIES;    SEMIMAGNETIC SEMICONDUCTORS;    ANISOTROPIC SUPEREXCHANGE;    ELECTRONIC-STRUCTURE;    STEPS;    INSULATORS;    FIELDS;    CD1-XMNXSE;    ZN1-XMNXSE;   

DOI  :  10.1103/PhysRevB.90.075205

来源: SCIE

【 摘 要 】

Exchange integrals between nearest-neighbor (NN) transition metal ions in II-VI diluted magnetic semiconductors (DMSs) are calculated within a local superexchange model, which includes orbital-dependent transfer, on-site Coulomb repulsion and Hund's exchange between 3d electrons, and ligand field effects. This extended model gives a quantitative account for the available experimental data on the NN exchange constants in all II-VI DMS family (wurtzite and zinc-blende) doped by cobalt or manganese. As expected, all obtained exchange integrals are antiferromagnetic. Remarkably, the model input parameters are taken directly from the photoemission spectroscopy. We show that in the case of Co-doped compounds, as compared to Mn-doped ones, the exchange process has at least two salient features. The first one is that the electron transfer between NN Co2+ 3d orbitals strongly depends on their symmetry positions in the crystal lattice. The second one is related to a peculiar virtual process, involving empty and occupied Co2+ 3d orbitals, which leads to an additional ferromagnetic contribution to the exchange constant. We argue that our systematic study of the superexchange opens a pathway toward an understanding of other exchange mechanisms occurring in DMSs.

【 授权许可】

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