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

Based upon ab initio electronic structure calculations by the Korringa -Kohn -Rostoker coherentpotential approximation (KKR-CPA) method within the local-density approximation (LDA), we propose a unified physical picture of magnetism and an accurate calculation method of Curie temperature (T C ) in dilute magnetic semiconductors (DMSs) in II -VI and III -V compound semiconductors. We also propose the unified physical picture of magnetism in the DMS, where ferromagnetic Zener's double-exchange mechanism (or Zener's p -d exchange mechanism) caused by the partially occupied impurity band and anti-ferromagnetic super-exchange mechanism (or ferromagnetic super-exchange mechanism) is competing to determine the magnetic states in the DMS. We propose that the three-dimensional 3D Dairisekiphase and one-dimensional 1D Konbu-phase caused by spinodal nano-decomposition are responsible for high-T C phase in the inhomogeneous system. We propose the new methodology to go beyond LDA to describe the highly correlated electron system by taking into account the self-interaction correction (SIC) to the LDA. the quantal phase (or Berry's phase) and nano-dynamics of spin, charge and atoms in the nano-structures of semiconductors.In order to boost the research on semiconductor nano-spintronics dramatically, we need to realize the high-temperature ferromagnetism (a few times higher-T C than the room temperature) with dilute magnetic semiconductor (DMS) nano-structures for the application of high-density (Tera-bit density per inch 2 ), high-speed (Tera-Hz switching), and low-power consumption (non-volatile memory) electronics. In spintronics application, magnetic properties may be carried by conventional metallic ferromagnets (Fe, Co and Ni) or dilute magnetic semiconductors (DMS) such as (Ga,Mn)As or (In,Mn)Sb. These materials are metallic or bad-metallic systems, therefore, we cannot control the magnetic properties by an electric field through the application of gate voltage. We need to develop the new control method of spin by electric field in semiconductors, carrier controlled ferromagnetism, spin injection into nanostructures, spin correction, spin manipulations, and spin detection, if we seriously want to develop a new class of electronics by semiconductor nano-spintronics to go beyond the silicon CMOS nanotechnology. To do so, self-controlled growth-positioning by the seeding, self-assembled and self-organized fabrication method of nano-scale-size ferromagnets (nano-magnets) in semiconductor matrix is absolutely necessary. This is the only method to control the spin by electric field in order to realize the new class of electronics by controlling the spin and charge degrees of freedom of electrons in the semiconductors. These new fabrication method of nano-magnets in semiconductor matrix permit the real application of semiconductor nano-spintronics [1], such as colossal or giant magneto-resistant memory, high sensitive field sensors, spin transistors, reconfigurable logic and quantum information and communication processing. In t...

Based on the microscopic mechanisms of (1) charge-excitation-induced negative effective U in s 1 or d 9 electronic configurations, and (2) exchange-correlation-induced negative effective U in d 4 or d 6 electronic configurations, we propose a general rule and materials design of negative effective U system in itinerant (ionic and metallic) system for the realization of high-T c superconductors. We design a T c -enhancing layer (or clusters) of charge-excitation-induced negative effective U connecting the superconducting layers for the realistic systems.In order to realize a new-class of high-T c superconductors, we need to design and realize an itinerant (ionic and metallic) system carrying a large negative effective-correlation energyis a total energy of an N electron system. In addition to both Anderson's mechanism for a negative effective U mechanism 1) induced by Jahn-Teller lattice distortion and the exchange-correlation-induced negative effective U (ECI-NEU) mechanism proposed by Katayama-Yoshida and Zunger, 2)here, we propose a new universal class of microscopic mechanism of NEU caused by chargeexcitation-induced NEU (CEI-NEU) from s-to p-orbital, or, d-to s-orbital in an ionic metal.The NEU interaction between two electrons generally leads to a charge-density wave (CDW) by charge disproportionation, or superconductivity (SC) by attractive pairing-interaction, or a spin-density wave (SDW) by an exchange-correlation interaction. In this paper, we propose a general rule on chemical trends for NEU system in order to design a new-class of high-T c superconductor, which is always competing with a CDW or SDW state.The total energy E(N ) of N electron system shows normally a convexity as a function of N due to the repulsive correlation energy ofbetween two electrons, therefore U > 0 guarantees a stability of the N electron system in the thermal equilibrium (see Fig.1). As is depicted schematically in

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