A. Yanase

The origin of the helical spin density wave in MnSi

Abstract By using a symmetry consideration, it is shown that an itinerant electron ferromagnet with no inversion symmetry is unstable against a helical spin density wave (HSDW) if a magnetic anisotropy energy is sufficiently small. The spin-orbit interaction is important to the stability of this HSDW. Only one of the clockwise and counterclockwise HSDWs is realized. The long and isotropic period of the HSDW in MnSi is explained successfully on this standpoint.

New interpretation of the de Haas-van Alphen signals of LaB6

Abstract A new model for the Fermi surface of LaB6 is proposed. It consists of spherical balls at X points connected by the short necks, instead of the slender necks previously considered, and the small ellipsoid-electron-pockets which are elongated along the Σ axes and overlap on the necks. Angular variations of frequencies and intensities of the de Haas-van Alphen signals are calculated. Accumulated data including recent acoustic measurement are explained consistently. The model is obtained by displacing the unoccupied 4f levels upward from those of the self-consistent band calculation. This indicates the importance of the correction to the local density approximation for the 4f states.

DE Haas-van Alphen effects on La(Sb, Bi) and Ce(Sb, Bi)

Abstract De Haas-van Alphen effects on LaSb and CeSb were measured. The calculated energy band structure in LaSb agrees with the experimental results. Experimental results of CeSb support strongly the p-f mixing theory.

Electronic structure of CaB6

The calcium hexaboride, CaB6, is a typical semiconducting metal hexaboride. Here two self-consistent APW calculations of its electronic energy bandstructure are reported, in the muffin-tin approximation and in the warped muffin-tin approximation. In both calculations, the local-spin-density approximation is used and the relativistic effects are taken into account. The bandstructure of the muffin-tin approximation is semimetallic. The non-muffin-tin corrections in the warped muffin-tin approximation tends to cause a small, direct energy gap between the valence and conduction bands at the X points in the simple cubic Brillouin zone. The magnitude of the energy gap to 0.3 eV, in reasonable agreement with the experimental value, 0.4 eV, suggested by the temperature dependence of the electrical resistivity. The calculated result for the density of states agrees reasonably well with an experimental result for the XPS spectrum.

Slater-Koster tables for f electrons

By representing f orbitals by cubic harmonics, overlap (or energy) integrals for f electrons have been calculated in terms of two-centre integrals. Results of s-f, p-f, d-f and f-f integrals are useful in making the tight-binding calculation as an interpolation method for substances with rare-earth or actinide elements.

Electronic energy band structure of MnSi

Abstract The electronic energy band structure of the intermetallic compound MnSi, a typical itinerant electron magnet, is calculated by a self-consistent APW method. The density of states at Fermi level is high (148 states/Ryd cell). This is consistent with the magnetic properties of MnSi.

Electronic structure of Sr monochalcogenides

Reports some results of a non-relativistic, self-consistent APW calculation of the electronic energy band structure for a series of Sr monochalcogenides, i.e. SrO, SrS, SrSe and SrTe, with the Slater exchange potential. The trend of the calculated results for the energy gap between the conduction and valence bands agrees well with the experimental results obtained by optical absorption measurements. Quantitatively, however, this calculation leads to values of the energy gap which are too small.

Energy bandstructure of YB12 and LuB12

Abstract Because of the proper reference materials for a new valence fluctuating system, YbB12, self-consistent calculations of the energy bandstructure of YB12 and LuB12 are carried out by using the usual RAPW method. Some correction in the potential for the 4f state is necessary. The p-f mixing parameters are estimated to be (pf σ) = 0.015 Ryd and (pf π) = -0.005 Ryd.

Electronic structure of MnP

The manganese phosphide, MnP, is a typical 3d intermetallic compound. The authors report a self-consistent APW calculation of the spin-polarised energy band structure for MnP. A one-electron potential is constructed by the local-spin-density approximation. For a minority spin electron, bands near the Fermi energy, EF, consist mainly of Mn d states and have a high density of states. Bands for a minority spin electron have a low density of states at EF. The calculated results for the total density of states satisfactorily explain the UPS spectrum and the electronic specific heat. The calculated spin moment per formula is 1.2 mu B and is in good agreement with the experimental value of 1.3 mu B.

A model for unusual magnetic anisotropy of Ce pnictides

Unusually strong magnetic anisotropies in CeSb and CeBi are accounted for by the anisotropic mixing mechanism between the 4f states and the valence bands. The anisotropy energy of CeSb is calculated using the valence bands obtained by the APW band calculations and good agreement with the observed large anisotropy is obtained. This mechanism is consistent with the fact that no such strong anisotropy is found in light Ce pnictides.