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We investigate the interaction of two Mn ions in the dilute magnetic semiconductor GaMnAs using the variational envelope wave function approach within the framework of six band model of the valence band. We find that the effective interaction between the Mn core spins at a typical separation d is strongly anisotropic for active Mn concentrations less than x = 1.3%, but it is almost isotropic for shorter distances (d < 13A). As a result, in unannealed and strongly compensated samples strong frustration effects must be present. We also verify that an effective Hamiltonian description can be used in the dilute limit, x < 1.3%, and extract the parameters of this effective Hamiltonian.
The electronic structure is found to be understandable in terms of free-atom term values and universal interorbital coupling parameters, since self-consistent tight-binding calculations indicate that Coulomb shifts of the d-state energies are small.
X-ray amorphous manganese oxides were prepared by reduction of sodium permanganate by lithium iodide in aqueous medium (MnOx-I) and by decomposition of manganese carbonate at moderate temperature (MnOx-C). TEM showed that these materials are not amor
We describe the ground- and excited-state electronic structure of bulk MnO and NiO, two prototypical correlated electron materials, using coupled cluster theory with single and double excitations (CCSD). As a corollary, this work also reports the fir
We report crystal structure, electronic structure, and magnetism of manganese tetraboride, MnB4, synthesized under high-pressure high-temperature conditions. In contrast to superconducting FeB4 and metallic CrB4, which are both orthorhombic, MnB4 fea
Optical properties of ZnMnO layers grown at low temperature by Atomic Layer Deposition and Metalorganic Vapor Phase Epitaxy are discussed and compared to results obtained for ZnMnS samples. Present results suggest a double valence of Mn ions in ZnO l