International audienceThis review summarizes recent first-principles investigations of the electronic structure and magnetism of dilute magnetic semiconductors (DMSs), which are interesting for applications in spintronics. Details of the electronic structure of transition-metal-doped III-V and II-VI semiconductors are described, especially how the electronic structure couples to the magnetic properties of an impurity. In addition, the underlying mechanism of the ferromagnetism in DMSs is investigated from the electronic structure point of view in order to establish a unified picture that explains the chemical trend of the magnetism in DMSs. Recent efforts to fabricate high-TC DMSs require accurate materials design and reliable TC predictions for the DMSs. In this connection, a hybrid method (ab initio calculations of effective exchange interactions coupled to Monte Carlo simulations for the thermal properties) is discussed as a practical method for calculating the Curie temperature of DMSs. The calculated ordering temperatures for various DMS systems are discussed, and the usefulness of the method is demonstrated. Moreover, in order to include all the complexity in the fabrication process of DMSs into advanced materials design, spinodal decomposition in DMSs is simulated and we try to assess the effect of inhomogeneity in them. Finally, recent works on first-principles theory of transport properties of DMSs are reviewed. The discussion is mainly based on electronic structure theory within the local-density approximation to density-functional theory

Materials design of new functional diluted magnetic semiconductors (DMSs) is presented based on first principles calculations. The stability of the ferromagnetic state in ZnO-, ZnS-, ZnSe-, ZnTe-, GaAs-and GaN-based DMSs is investigated systematically and it is suggested that V-or Cr-doped ZnO, ZnS, ZnSe and ZnTe are candidates for high-T C ferromagnetic DMSs. V-, Cr-or Mn-doped GaAs and GaN are also candidates for high-T C ferromagnets. It is also shown that Fe-, Co-or Ni-doped ZnO is ferromagnetic. In particular, the carrier-induced ferromagnetism in ZnO-based DMSs is investigated and it is found that their magnetic states are controllable by changing the carrier density. The origin of the ferromagnetism in the DMSs is also discussed.

Ferromagnetism of ZnO-based magnetic semiconductors was investigated by ab initio calculations based on the local density approximation. In a system of Mn atom doped ZnO, the ferromagnetic ordering of Mn magnetic moments was induced by hole doping. It was also found that 3d transition metal atoms of V, Cr, Fe, Co and Ni showed the ferromagnetic ordering of their magnetic moments in ZnO without any additional carrier doping treatments. Appearance of the ferromagnetism in these systems suggests possibility for a fabrication of a transparent ferromagnet which will have great impact on industrial applications in magneto optical devices.

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The magnetic properties of dilute magnetic semiconductors (DMSs) are calculated from first-principles by mapping the ab initio results on a classical Heisenberg model. By using the Korringa-Kohn-Rostoker coherent-potential approximation (KKR-CPA) method within the local-density approximation, the electronic structure of (Ga, Mn)N and (Ga, Mn)As is calculated. Effective exchange coupling constants J ij 's are determined by embedding two Mn impurities at sites i and j in the CPA medium and using the J ij formula of Liechtenstein et al. [J. Magn. Magn. Mater. 67, 65 (1987)]. It is found that the range of the exchange interaction in (Ga, Mn)N, being dominated by the double exchange mechanism, is very short ranged due to the exponential decay of the impurity wave function in the gap. On the other hand, in (Ga, Mn)As, where p-d exchange mechanism dominates, the interaction range is weaker but long ranged, because the extended valence hole states mediate the ferromagnetic interaction. Curie temperatures (T C 's) of DMSs are calculated by using the mean-field approximation (MFA), the random-phase approximation, and the, in principle exact, Monte Carlo method. It is found that the T C values of (Ga, Mn)N are very low since, due to the short-ranged interaction, percolation of the ferromagnetic coupling is difficult to achieve for small concentrations. The MFA strongly overestimates T C . Even in (Ga, Mn)As, where the exchange interaction is longer ranged, the percolation effect is still important and the MFA overestimates T C by about 50%-100%. Dilute magnetic semiconductors (DMSs), such as (In, Mn)As and (Ga, Mn)As discovered by Munekata et al. and Ohno et al., have been well investigated as hopeful materials for spintronics. 1 Curie temperatures (T C 's) of these DMSs are well established 1-3 and some prototypes of spintronics devices have been produced based on these DMSs. The magnetism in these DMSs are theoretically investigated and it is known that the ferromagnetism in these systems, as well as (Ga, Mn)Sb, can be well described by Zener's p-d exchange interaction, due to the fact that the majority of d states lies energetically in the lower part of the valence band.4 Dietl et al. 5 and MacDonald et al. 6 explained many physical properties of (Ga, Mn)As based on the p-d exchange model, and first-principles calculations by Sato et al. showed that the concentration dependence of T C in (Ga, Mn)As was well understood by the p-d exchange interaction if a correction to the local-density approximation (LDA) is simulated by the LDA+ U method with U = 4 eV. 4 While these p-d exchange systems, in which the d states of Mn impurities are practically localized, are well understood, there exist an even larger class of systems where the d levels lie in the gap exhibiting impurity bands for sufficiently large concentrations. To these impurity band systems belong (Ga, Mn)N, (Ga, Cr)N, (Ga, Cr)As, (Zn, Cr)Te, (Zn, Cr)Se, and many others, as shown by first-principles calculations. 7Most of these systems are controversially discussed ...