Search

To study the temperature dependence of magnetic properties of permanent magnets, methods of treating the thermal fluctuation causing the thermal activation phenomena must be established. To study finite-temperature properties quantitatively, we need atomistic energy information to calculate the canonical distribution. In the present review, we report our recent studies on the thermal properties of the Nd2Fe14B magnet and the methods of studying them. We first propose an atomistic Hamiltonian and show various thermodynamic properties, for example, the temperature dependences of the magnetization showing a spin reorientation transition, the magnetic anisotropy energy, the domain wall profiles, the anisotropy of the exchange stiffness constant, and the spectrum of ferromagnetic resonance. The effects of the dipole–dipole interaction (DDI) in large grains are also presented. In addition to these equilibrium properties, the temperature dependence of the coercivity of a single grain was studied using the stochastic Landau-Lifshitz-Gilbert equation and also by the analysis of the free energy landscape, which was obtained by Monte Carlo simulation. The upper limit of coercivity at room temperature was found to be about 3 T at room temperature. The coercivity of a polycrystalline magnet, that is, an ensemble of interactinve grains, is expected to be reduced further by the effects of the grain boundary phase, which is also studied. Surface nucleation is a key ingredient in the domain wall depinning process. Finally, we study the effect of DDI among grains and also discuss the distribution of properties of grains from the viewpoint of first-order reversal curve.

First-principles calculation based on density functional theory is a powerful tool for understanding and designing magnetic materials. It enables us to quantitatively describe magnetic properties and structural stability, although further methodological developments for the treatment of strongly correlated 4f electrons and finite-temperature magnetism are needed. Here, we review recent developments of computational schemes for rare-earth magnet compounds, and summarize our theoretical studies on Nd2Fe14B and RFe12-type compounds. Effects of chemical substitution and interstitial dopants are clarified. We also discuss how data-driven approaches are used for studying multinary systems. Chemical composition can be optimized with fewer trials by the Bayesian optimization. We also present a data-assimilation method for predicting finite-temperature magnetization in wide composition space by integrating computational and experimental data., Graphical abstract

We present spin-wave dispersion in Sm(Fe$_{1-x}$Co$_x$)$_{12}$ calculated based on first-principles. Anisotropy in the lowest branch of the spin-wave dispersion around the $\Gamma$ point is discussed. Spin-waves propagate more easily along $a^*$-axis than along $c^*$-axis, especially in SmFe$_{12}$. We also compare values of the spin-wave stiffness with those obtained from an experiment. The calculated values are in good agreement with the experimental values., Comment: 15 pages, 6 figures

We propose a data assimilation method for evaluating the finite-temperature magnetization of a permanent magnet over a high-dimensional composition space. Based on a general framework for constructing a predictor from two data sets including missing values, a practical scheme for magnetic materials is formulated in which a small number of experimental data in limited composition space are integrated with a larger number of first-principles calculation data. We apply the scheme to ${({\mathrm{Nd}}_{1\ensuremath{-}\ensuremath{\alpha}\ensuremath{-}\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}}{\mathrm{Pr}}_{\ensuremath{\alpha}}{\mathrm{La}}_{\ensuremath{\beta}}{\mathrm{Ce}}_{\ensuremath{\gamma}})}_{2}{({\mathrm{Fe}}_{1\ensuremath{-}\ensuremath{\delta}\ensuremath{-}\ensuremath{\zeta}}{\mathrm{Co}}_{\ensuremath{\delta}}{\mathrm{Ni}}_{\ensuremath{\zeta}})}_{14}\mathrm{B}$. The magnetization in the whole $(\ensuremath{\alpha},\ensuremath{\beta},\ensuremath{\gamma},\ensuremath{\delta},\ensuremath{\zeta})$ space at arbitrary temperature is obtained. It is shown that the Co doping does not enhance the magnetization at low temperatures, whereas the magnetization increases with increasing $\ensuremath{\delta}$ above 320 K.

We theoretically investigate spin-wave dispersion in rare-earth magnet compounds by using first-principles calculations and a method we call the reciprocal-space algorithm. The value of the calculated exchange stiffness for ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ is within the range of reported experimental values. We find that the exchange stiffness is considerably anisotropic when only short-range exchange couplings are considered, whereas inclusion of long-range couplings weakens the anisotropy. In contrast, $R{\mathrm{Fe}}_{11}\mathrm{Ti}$ ($R=\mathrm{Y},\mathrm{Nd},\mathrm{Sm}$) shows large anisotropy in the exchange stiffness.

The surface magnetism of Fe(001) was studied in an atomic layer-by-layer fashion by using the in situ iron-57 probe layer method with a synchrotron Mossbauer source. The observed internal hyperfine field H_{int} exhibits a marked decrease at the surface and an oscillatory behavior with increasing depth in the individual upper four layers below the surface. The calculated layer-depth dependencies of the effective hyperfine field |H_{eff}|, isomer shift δ, and quadrupole shift 2ϵ agree well with the observed experimental parameters. These results provide the first experimental evidence for the magnetic Friedel oscillations, which penetrate several layers from the Fe(001) surface.

$3d\text{\ensuremath{-}}4f$ intermetalic compounds with heavy rare-earth elements show first-order phase transitions in high magnetic fields due to the competition between the exchange interaction and the magnetocrystalline anisotropy. However, the microscopic picture of the field-induced noncollinear magnetic structures remains elusive. Here we report the direct experimental observation of the coherent stepwise rotation of the $3d$ and $4f$ magnetic moments of the uniaxial hard ferrimagnet ${\mathrm{TmFe}}_{5}{\mathrm{Al}}_{7}$ by using soft x-ray magnetic circular dichroism in pulsed magnetic fields up to 25 T. The element- and shell-selective moments show a transition from the collinear ferrimagnet toward the forced ferromagnetic state via a canted phase, which is explained by a two-sublattice model.

We have developed a full potential Korringa-Kohn-Rostoker (KKR) Green function method. Three improvements which make the full potential treatment efficient and practical are reported. One is a method for constructing the Green function which satisfies the Wronskian relation exactly. The second is including the contribution of the non-spherical part of the potential in the wavefunctions correctly by use of a modified recursive integral equation. Thirdly, we propose a method that completely eliminates the contribution of irregular solutions of the Schrodinger equation to charge/spin densities. In order to check the reliability of the method, we calculated the electric field gradient (EFG), which is sensitive to how the potential is treated. We have performed EFG calculations for hcp metals and sp impurities in Zn and Cd with the present method. The results are in good agreement with experimental data and show that the full potential KKR method is reliable enough for EFG calculations.

We present a data set of calculated Curie temperatures for the main-phase compounds of rare-earth permanent magnets. We employ ab initio electronic structure calculations for the itinerant ferromagnetism and an effective spin model for the finite-temperature magnetism. Curie temperatures are derived on the basis of a classical Heisenberg model mapped via Liechtenstein's formula for atomic-pair-wise exchange couplings. Relative trends with respect to the species of rare-earth elements in calculated Curie temperatures for R2Fe14B are in agreement with experimental trends. Quantitative comparison between calculation and experimental data found in the literature point to an effective range of the exchange couplings imposing a limit on the validity range of the effective spin model., 5 pages, 7 figures, to be published on Phys. Rev. B

Calculations based on density functional theory conclude that the plausible upper limits of saturation magnetic polarization, magnetic transition temperature, and the magnetocrystalline anisotropy constant of permanent magnet materials could be ∼2.7 T, ∼2000 K, and ∼1000 MJ m−3, respectively. It is suggested that a possible strategy to reach these values for high-performance permanent magnets is to design Fe-based magnets containing a small amount of light rare earth elements, together with some additional elements including V, Cr, Co, Ni, and possibly typical elements as interstitials. The idea of creating high-performance permanent magnets without rare earth elements can be dispensed with.

The Korringa–Kohn–Rostoker (KKR) method combined with the coherent potential approximation (CPA; KKR-CPA) and linear response theory is applied to first-principles calculation of the Seebeck coefficients of pure metals. The main objective is to develop a practical first-principles scheme that can calculate the conductivities and Seebeck coefficients of metallic systems at finite temperature. Thus, it is necessary to include the effects of electron-phonon scattering, which plays a crucial role at finite temperature, particularly for ordered-structure systems where the conductivity diverges at T = 0 K . The approach combines three components: linear response theory in the framework of the KKR method; phonon calculations; and an alloy analogy applied to the local static phonons using the KKR-CPA. The calculated Cu resistivity and Seebeck coefficients for various transition-metal elements at finite temperature show reasonably good overall agreement with experiment. The present approach provides a framework applicable to a wide range of materials, including pure metals, compounds, doped semiconductors, ordered and disordered alloys, opening up the possibilities of computational design of useful thermoelectric materials.

The thermal conductivity of the Earth's core can be estimated from its electrical resistivity via the Wiedemann–Franz law. However, previously reported resistivity values are rather scattered, mainly due to the lack of knowledge with regard to resistivity saturation (violations of the Bloch–Gruneisen law and the Matthiessen's rule). Here we conducted high-pressure experiments and first-principles calculations in order to clarify the relationship between the resistivity saturation and the impurity resistivity of substitutional silicon in hexagonal-close-packed (hcp) iron. We measured the electrical resistivity of Fe–Si alloys (iron with 1, 2, 4, 6.5, and 9 wt.% silicon) using four-terminal method in a diamond-anvil cell up to 90 GPa at 300 K. We also computed the electronic band structure of substitutionally disordered hcp Fe–Si and Fe–Ni alloy systems by means of Korringa–Kohn–Rostoker method with coherent potential approximation (KKR-CPA). The electrical resistivity was then calculated from the Kubo–Greenwood formula. These experimental and theoretical results show excellent agreement with each other, and the first principles results show the saturation behavior at high silicon concentration. We further calculated the resistivity of Fe–Ni–Si ternary alloys and found the violation of the Matthiessen's rule as a consequence of the resistivity saturation. Such resistivity saturation has important implications for core dynamics. The saturation effect places the upper limit of the resistivity, resulting in that the total resistivity value has almost no temperature dependence. As a consequence, the core thermal conductivity has a lower bound and exhibits a linear temperature dependence. We predict the electrical resistivity at the top of the Earth's core to be 1.12 × 10 − 6 Ω m , which corresponds to the thermal conductivity of 87.1 W/m/K. Such high thermal conductivity suggests high isentropic heat flow, leading to young inner core age (

In this study, we calculate the temperature-dependent electronic structures and transport properties of the Heusler alloy Co2MnSi on the basis of the Korringa–Kohn–Rostoker Green's function method combined with the coherent potential approximation (CPA). Temperature effects often have a significant influence on the spin-polarization properties of Heusler alloys. To incorporate the contributions of temperature effects, we first consider lattice vibrations and spin fluctuations. Using CPA, we can replace them with random displacements due to local phonons and local magnetic moment disorders, respectively. In the Co2MnSi Heusler alloy, we found that the band structures are smeared by the electron–phonon scattering process and the half-metallic property is eliminated by magnon excitations from the spin-up to spin-down states. Furthermore, we can estimate the electrical resistivity as a function of temperature in the scheme of linear response theory. Including the local phonon disorder, local moment disorder, and Mn–Co antisite disorder in CPA, we can reproduce the temperature-dependent resistivity observed by experiments.

We calculate intersite magnetic couplings for Sm$_2$Fe$_{17}$, Nd$_2$Fe$_{14}$ and Nd$_2$Fe$_{14}$X (X = B, C, N, O, F) using Liechtenstein's formula on the basis of first-principles calculation, and analyze them to investigate the Curie temperature of Sm$_2$Fe$_{17}$ and Nd$_2$Fe$_{14}$B. We find that the magnetic coupling in the dumbbell bond is strongly ferromagnetic in our calculation, which is against a previous conjecture explaining the low Curie temperature for Sm$_2$Fe$_{17}$. The calculated values of the couplings explain the experimentally observed difference in the Curie temperature of Sm$_2$Fe$_{17}$ and Nd$_2$Fe$_{14}$B. We also address boron's effects on the Curie temperature of Nd$_2$Fe$_{14}$B, especially in connection with Kanamori's theory of cobaltization., 5 pages; 7 figures

Nonlinear optical frequency conversion has been challenged to move down to the extreme ultraviolet and x-ray region. However, the extremely low signals have allowed researchers to only perform transmission experiments of the gas phase or ultrathin films. Here, we report second harmonic generation (SHG) of the reflected beam of a soft x-ray free-electron laser from a solid, which is enhanced by the resonant effect. The observation revealed that the double resonance condition can be met by absorption edges for transition metal oxides in the soft x-ray range, and this suggests that the resonant SHG technique can be applicable to a wide range of materials. We discuss the possibility of element-selective SHG spectroscopy measurements in the soft x-ray range.

Ab initio electronic structure calculation of a series of Co2FeAl1−xSix Heusler alloys has been performed, using the Korringa–Kohn–Rostoker-coherent potential approximation method to explain experimental 59Co NMR spectra. Two prominent features are explained semi-quantitatively—a global shift of the 59Co resonance line due to alloying with Al and Si atoms in Co2FeAl1−xSix, and the effect of local disorder in creating distinct satellite lines of 59Co NMR in Co2FeAl. The importance is stressed of the positive contribution to the 59Co hyperfine field from valence electron polarization, which emerges from the half-metallic band structure inherent in Co-based Heusler alloys.

We studied the properties of domain walls (DWs) of the Neodymium magnet, ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$. Applying an atomistic model, in which the magnetic moments of all atoms and exchange interactions were determined by a first-principles calculation (Korringa-Kohn-Rostoker Green's function method), we performed a Monte Carlo simulation for two types of DW, i.e., moving along the $a$ axis and along the $c$ axis, which are classified into a Bloch-type wall and a Neel-type wall, respectively. We found that the shapes of the DWs of both types are described well by those derived from the continuum model used in micromagnetics. We show that the estimated DW widths are very close to the experimentally evaluated ones. Furthermore, we discovered that the width of the latter type is smaller than that of the former type. We also investigated the temperature dependence of the DW width and found that at higher temperatures it becomes larger and the magnitude of the magnetization becomes smaller, which agrees with experimental observations.

The optimized effective potential (OEP) method is a promising technique for calculating the ground state properties of a system within the density functional theory. However, it is not widely used as its computational cost is rather high and, also, some ambiguity remains in the theoretical framework. In order to overcome these problems, we first introduced a method that accelerates the OEP scheme in a static RPA-level correlation functional. Second, the Krieger-Li-Iafrate (KLI) approximation is exploited to solve the OEP equation. Although seemingly too crude, this approximation did not reduce the accuracy of the description of the magnetic transition metals (Fe, Co, and Ni) examined here, the magnetic properties of which are rather sensitive to correlation effects. Finally, we reformulated the OEP method to render it applicable to the direct RPA correlation functional and other, more precise, functionals. Emphasis is placed on the following three points of the discussion: i) Level-crossing at the Fermi surface is taken into account; ii) eigenvalue variations in a Kohn-Sham functional are correctly treated; and iii) the resultant OEP equation is different from those reported to date., 18 pages, 3 figures. This is an author-created, un-copyedited version of an article accepted for publication in Journal of Physics: Condensed Matter. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0953-8984/27/11/115502

We present a first-principles investigation of NdFe$_{12}$ and NdFe$_{12}$X (X = B, C, N, O, F) crystals with the ThMn$_{12}$ structure. Intersite magnetic couplings in these compounds, so-called exchange couplings, are estimated by Liechtenstein's method. It is found that the Nd--Fe couplings are sensitive to the interstitial dopant X, with the Nd--Fe(8j) coupling in particular reduced significantly for X = N. This suggests that the magnetocrystalline anisotropy decays quickly with rising temperature in the X = N system although nitrogenation has advantages over the other dopants in terms of enhancing low-temperature magnetic properties. The Curie temperature is also calculated from the magnetic couplings by using the mean field approximation. Introduction of X enhances the Curie temperature, with both structural changes and chemical effects found to play important roles in this enhancement., 18 pages, 11 figures; data added to Appendix sections

The high-field NMR shift of 59Co in the ferromagnetic state of the Heusler alloy Co2TiGa has been calculated to be +0.65% by local density approximation (LDA) involving the spin–orbit interaction b...

We investigate the effects of magnetic inhomogeneities and thermal fluctuations on the magnetic properties of a rare-earth intermetallic compound, ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$. The constrained Monte Carlo method is applied to a ${\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}$ bulk system to realize the experimentally observed spin reorientation and magnetic anisotropy constants ${K}_{m}^{\mathrm{A}}\phantom{\rule{4pt}{0ex}}(m=1,2,4)$ at finite temperatures. Subsequently, it is found that the temperature dependence of ${K}_{1}^{\mathrm{A}}$ deviates from the Callen-Callen law, ${K}_{1}^{\mathrm{A}}(T)\ensuremath{\propto}M{(T)}^{3}$, even above room temperature, ${T}_{\mathrm{R}}\ensuremath{\sim}300\phantom{\rule{4pt}{0ex}}\mathrm{K}$, when the Fe (Nd) anisotropy terms are removed to leave only the Nd (Fe) anisotropy terms. This is because the exchange couplings between Nd moments and Fe spins are much smaller than those between Fe spins. It is also found that the exponent $n$ in the external magnetic field ${H}_{\mathrm{ext}}$ response of barrier height ${\mathcal{F}}_{\mathrm{B}}={\mathcal{F}}_{\mathrm{B}}^{0}{(1\ensuremath{-}{H}_{\mathrm{ext}}/{H}_{0})}^{n}$ is less than 2 in the low-temperature region below ${T}_{\mathrm{R}}$, whereas $n$ approaches 2 when $Tg{T}_{\mathrm{R}}$, indicating the presence of Stoner-Wohlfarth-type magnetization rotation. This reflects the fact that the magnetic anisotropy is mainly governed by the ${K}_{1}^{\mathrm{A}}$ term in the $Tg{T}_{\mathrm{R}}$ region.

In order to teach the accumulated knowledge of nanoscience, nanoengineering and nanotechnology to graduate school students and young scientists with the sense of public engagement, Osaka University started from 2004 to prepare and offer various kinds of education and training programs such as trans-disciplinary graduate-school minor program, evening course refresher program, short-term international research training program, etc. It offers a series of lectures, partly broadcasted live to satellite classrooms. In addition, the students can join intensive hands-on training programs using modern facilities, allowing them to design, fabricate, measure, characterize and functionalize nanomaterials and nanodevices. In addition, there are four specially designed lectures and research training programs aimed for nanocommunication including social, legal and ethical relationship: “Nanotechnology Career-up Lectures”, “Social Engagement on Nanotechnology”, “Road Map Design on Nanotechnology”, and “Project- Aimed Learning and Training Programs (PAL)”. The outline of the whole programs is described together with the specialized programs for nanocommunication.

We review the progress in the recent development of the relativistic optimized effective potential (ROEP) method within spin-density functional theory. The ROEP-equations for spin-polarized systems are derived and their application to open-shell atoms using the exact exchange approximation for the exchange correlation-functional is presented. Further, we expand the ROEP framework to treat extended systems within the KKR-multiple scattering formalism. We illustrate the application of the theory to open-shell free atoms and solids.

The structural and magnetic properties of diluted magnetic III-V and II-VI semiconductors (DMS) have been investigated using ab initio simulations techniques based on density functional theory and the generalized gradient approximation (GGA) for the exchange-correlation term. In order to achieve an agreement with spectroscopic data of the electronic structure, it is necessary to employ methods which go beyond the standard implementation of density funcional theory allowing for a better description of Coulomb correlations in the poorly screened rather open ionic structures of the materials. As an example, we give a detailed description of Codoped ZnO in the wurtzite lattice.

A way of nuclear spin manipulation using an interface of diluted magnetic semiconductors (DMSs) is proposed. The hyperfine field at an impurity site in the interface of a DMS and a base substance can be controlled by applying the external electric field. It is because that the electric field changes the spin density of carriers in the s state at the impurity site. On the basis of first-principles electronic structure calculation, we investigated the electric-field dependence of the hyperfine field at the impurity site. We show that the hyperfine field is dramatically changed by an external electric field when no clear magnetic impurity band is formed in the band gap. [DOI: 10.1380/ejssnt.2008.7]

The electronic and magnetic properties of Mn1−xCrxTe of NiAs-type and zinc-blend type structures are theoretically investigated using the first-principles KKR-CPA method. It is concluded that at low concentration region of Cr, an antiferromagnetic state is the ground-state, while a ferrimagnetic state is more stable at higher concentration region of Cr in the both types of structures. In particular, a new type of half-metallic ferrimagnets is found in zinc-blend type Mn1−xCrxTe. On the other hand, a nearly half-metallic behavior is observed in NiAs-type Mn1−xCrxTe, where the Fermi level locates slightly above the minority spin band gap. The features of the half-metallicity of Mn1−xCrxTe in zinc-blend structure are also seen in the results of the conductivity calculations using the Kubo–Greenwood formula.

The spin-lattice relaxation times T1 for short-lived β emitters 25Al(I = 5/2, T1/2 = 7.2 s) and 28P(I = 3, T1/2 = 270 ms) in Pt were measured by means of the β-NMR technique. As a result, T1[25Al in Pt] = (1.1 \(^{+\ 0.7}_{-\ 0.3})\) s and T1[28P in Pt] >0.5 s were obtained at temperatures of 17 and 20 K, respectively. The Knight shifts were estimated from the Korringa relation, which were evaluated by comparing to the first principle calculations.

The Knight shift of a short lived β-emitting nucleus 12B (I = 1, T 1/2 = 20 ms) implanted into Pt has been measured as a function of temperature (140−600 K) by means of the β-NMR method. The relation between the Knight shift and the susceptibility for Pt was deduced, which shows the similar tendency to that for the case of 12B in Pd.

Half-metallic diluted antiferromagnetic semiconductors (HM-AF-DMSs) are magnetic materials that are half-metallic and yet do not exhibit magnetization. The remarkable features of these materials and the possible experimental verifications for determining whether or not a material is a HM-AF-DMS by the detection of hyperfine interactions are discussed on the basis of the first-principles calculations of the electronic structure.

Nuclear spin manipulation using an interface of diluted magnetic semiconductors (DMSs) is proposed. On the basis of the first-principles electronic structure calculation, we show that the hyperfine fields at an impurity site in the interface between a DMS and a base substance is dramatically changed by an external electric field. The electric field dependence of the hyperfine fields at the impurity nucleus in the interface of (InMn)As and (GaMn)As is examined.

The dc conductivity at T = 0 K of half-metallic diluted antiferromagnetic semiconductors and their super lattice is calculated by the use of the Kubo–Greenwood formula applied to the Korringa–Kohn–Rostoker (KKR) Green's function method and the coherent potential approximation in the framework of the local density approximation (LDA) of the density functional method (KKR-CPA-LDA). The calculated dc conductivity of superstructures composed of diluted antiferromagnetic semiconductors shows significant dependence on the magnetic structure of the superstructures. The mechanisms responsible for such behaviour are discussed on the basis of the first-principles calculation.

We propose a method to deal with the so-called near-field corrections to the solution of the Poisson equation for full-potential first-principles calculations using the exact two-center expansion for the inverse of the distance between two points. It is demonstrated that the method gives a very satisfying solution to the Poisson equation for plane-wave charge densities which can be solved analytically. The present method gives reasonable total energy for lattice distortions where the conventional multipole expansion gives large errors.

The magnetic and magnetocaloric properties of Ni–Co–Mn–(Ga, In, Sn) Heusler intermetallics are discussed on the basis of ab initio and Monte Carlo calculations. The main emphasis is on the different reference spin states and magnetic exchange coupling constants of high-temperature austenite and low-temperature martensite which are very important for the calculation of magnetocaloric effect. The origin of metamagnetic behavior is considered in the framework of orbital resolved magnetic exchange parameters of austenite and martensite. The decomposition of exchange constants on orbital contributions has shown that a strong ferromagnetic interaction of magnetic moments in austenite is caused by the more itinerant d-electrons with t2g states while a strong antiferromagnetic interaction in martensite is associated with the more localized eg states. In addition, the appearance of a paramagnetic gap between magnetically weak martensite and ferromagnetically ordered austenite can be realized because of strong competition of magnetic exchange interactions. As a result, large magnetization drop and giant inverse magnetocaloric effect can be achieved across the magnetostructural phase transition.

We present the electronic structures, magnetic exchange interactions and Curie temperature (TC) of GaMnN and GaMnAs calculated by self-interaction-corrected local-density approximation (LDA-SIC). In GaMnAs, the LDA-SIC results of TC do not differ so much from the LDA results. Both the LDA and LDA-SIC values are in a good agreement with the experimental data. In GaMnN, on the other hand, the ferromagnetic exchange interactions are enhanced due to the suppression of antiferromagnetic super-exchange interaction, resulting in TC higher than the LDA results. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The possibility of half-metallic diluted antiferromagnetic semiconductors of chalcopyrite-type structure codoped with 3d transition metal ions are investigated on the basis of first-principles electronic structure calculation. It is found that AgGaS2 and CuAlS2 co-doped with V-Co, Cr-Fe, Cr-Co, and V-Fe might be good candidates for half-metallic antiferromagnets. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We calculate the electronic structures of ZnO-based dilute magnetic semiconductors within the self-interaction-corrected local density approximation. The results are compared with those calculated within the standard local density approximation. We find the differences in the band gap energy, the energetic position of the Zn 3d bands, and the description of the transition-metal d bands.