Hisazumi Akai

Electronic Structure of Impurities in Ferromagnetic Iron. I. s, p Valence Impurities

The electronic structure of impurity atoms (atomic number Z =1–56) in ferromagnetic iron is calculated self-consistently by the Green function method in the local density approximation of the spin-density functional approach. The calculation * corresponds to an improvement and the extension of the previous work by Yoshida, Terakura and Kanamori. The mechanism proposed by them for the observed systematic variation in the hyperfine field and the nuclear spin-lattice relaxation time of impurity nuclei for substitutional impurities with Z ≥10 is confirmed on the basis of the present self-consistent calculation which is carried out systematically for the first time.

Electronic Structure of Impurities in Ferromagnetic Iron. II. 3d and 4d Impurities

The local magnetic moment M loc , the hyperfine field H hf and the nuclear spin-lattice relaxation time T 1 of 3 d and 4 d transition metal impurities in Fe are calculated in the framework of the Green function method and in the local spin density approximation (LSD). The calculation reproduces the observed major trends of M loc , H hf and T 1 quite well, though the calculated H hf shows a systematic deviation from the experimental values in the case of impurities whose magnetic moment couples parallel to the bulk magnetization. The mechanisms of the variation of these quantities are elucidated in the light of the present ab initio calculation.

Electronic Structure Ni–Pd Alloys Calculated by the Self-Consistent KKR-CPA Method

The electronic structure of disordered Ni–Pd alloys is investigated by means of the KKR method which is combined with the CPA and the local-spin-density approximation. Good overall agreements with the measurements are obtained for the magnetic moment distribution and for the hyperfine field at Ni nucleus. The origins of the large magnetic moment at Ni site (∼1.2 µ B ) and the positive hyperfine field on the Ni nucleus, both in Pd-rich region, are discussed in the light of the present calculation which can reproduce them quantitatively.

Electronic Structure of Impurities in Ferromagnetic Iron. III. Light Interstitials

A self-consistent calculation of the electronic structure of light impurities (µ + , H, He, …, F, Ne) at substitutional and interstitial sites in ferromagnetic iron is presented. The calculation is based on the KKR method with the impurity potential self-consistently determined by use of the local spin density functional formalism. The adiabatic potential of impurity around the center of a substitutional site is also calculated within the same framework with the result that it takes a maximum value at the center in the cases of µ + , H, B, C, N, O and F, a minimum one in the cases of He, Li and Ne and is quite flat in the case of Be. A qualitative argument is given on the mechanism underlying the variation of the adiabatic potential with atomic number. Experimental data on the hyperfine interaction of impurity nuclei are discussed in the light of these calculations to conclude plausible locations of impurities.

On the Disappearance of Ferromagnetism in Disordered Fe-Al Alloys

The magnetic properties of disordered Fe rich Fe-Al are investigated theoretically by using the coherent potential approximation (CPA) on the basis of the two different models. The self-consistent CPA calculation combined with the Korringa-Kohn-Rostoker method and the local spin density approximation is shown to reproduce the experimental result of the conceptration dependence of the bulk magnetization only for low Al concentration region. The ferromagnetism-to-spin glass second order transition at the critical Al concentration is obtained by the calculation on the basis of the tight binding model in which Fe atoms with magnetic moment antiparallel to the bulk magnetization are distinguished from Fe atoms with parallel moments. The calculated spin susceptibility well reproduces the experimental result.

Formulation of the Augmented Plane-Wave and Muffin-Tin Orbital Method

The augmented plane waves and the muffin-tin orbitals method (the PMT method) was proposed by Kotani and van Schilfgaarde in Phys. Rev. B 81, 125117 (2010). It is a mixed basis all-electron full-potential method, which uses two types of augmented waves simultaneously, in addition to the local orbitals. In this paper, this mixed basis method is reformulated on the basis of a new formalism named as the 3-component formalism, which is a mathematically transparent version of the additive augmentation originally proposed by Soler and Williams in Phys. Rev. B 47, 6784 (1993). Atomic forces are easily derived systematically. We discuss some problems in the mixed basis method and ways to manage them. In addition, we compare the method with the PAW method on the same footing. This PMT method is the basis for our new development of the quasiparticle self-consistent GW method in J. Phys. Soc. Jpn. 83, 094711 (2014), available as the \(\texttt{ecalj}\) package at github.

Monte Carlo analysis for finite-temperature magnetism of Nd 2 Fe 14 B permanent magnet

We investigate the effects of magnetic inhomogeneities and thermal fluctuations on the magnetic properties of a rare-earth intermetallic compound,

First-principles study of intersite magnetic couplings in NdFe12 and NdFe12X (X = B, C, N, O, F)

{\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}

Relevance of 4f-3d exchange to finite-temperature magnetism of rare-earth permanent magnets: An ab-initio-based spin model approach for NdFe12N

. The constrained Monte Carlo method is applied to a

Enhancement of Magnetism of Fe by Cr and V

{\mathrm{Nd}}_{2}{\mathrm{Fe}}_{14}\mathrm{B}