S Fujii

Hyperfine fields and electronic structures of the Heusler alloys Co2MnX (X=Al, Ga, Si, Ge, Sn)

Hyperfine fields and electronic structures were calculated by the KKR method to investigate the effects of the X atom on the magnetic properties of Co2MnX. The obtained magnetic moments of Co or Mn sites in Co2MnX are in good agreement with the experimental ones. Though the obtained hyperfine fields on Co or Mn sites are smaller in absolute value than the experimental ones, their trend is consistent with the experimental one. The hyperfine field on Mn sites is essentially determined by the magnetic moments on Mn sites themselves, but not that on Co sites. The relationship between the Co hyperfine field and the valence electron number of X atoms is discussed in terms of the obtained density-of-state.

Theoretical search for half-metalliic films of Co2MnZ (Z Si, Ge)

Abstract To search a half-metallic (HM) film, we calculated the energy band structures of the films of Co 2 MnZ (Z  Si, Ge) which were theoretically predicted to be HM in the bulk. The band structures of the (0 0 1) and (1 1 1) films show that whether the film becomes HM or not is conditional on its thickness and its surface and that the (1 1 1) film with the Z atom surface is appropriate as a FM film.

Magnetic and half-metallic properties of new Heusler alloys Ru2MnZ (Z Si, Ge, Sn and Sb)

Abstract Electronic structures of new Heusler alloys Ru 2 MnZ (Z  Si, Ge, Sn and Sb) were calculated to examine the magnetic properties. In this paper, it will be shown that an antiferromagnetic state is stable for these alloys, where the Mn magnetic moments are aligned ferromagnetically in the (111) plane and antiparallel along the [111] direction. It will also be shown that the alloys Ru 2 MnZ (Z  Si, Sb) can be half-metallic in a ferromagnetic phase.

Electronic structures and magnetic properties of Fe2P, Co2P and CoMnP

The electronic structures of the compounds Fe2P, Co2P and CoMnP are calculated by the LMTO method within the LSD approximation, not only for the orthorhombic structure but also for the hexagonal structure. The paramagnetic DOS are very similar for both structures. The values of the paramagnetic DOS at the Fermi level allow us to predict that Co2P exhibits ferromagnetism only in the hexagonal structure and that Fe2P exhibits ferromagnetism in both crystal structures. The theoretical results for the magnetic properties of CoMnP are in agreement with the experimental results. The site preference is also discussed together with the electron transfer from P atoms to 3d atoms.

Electronic structures and magnetic properties of Fe16X2 (X=B, C and N)

Electronic structures of Fe16X2 (X=B, C and N) were calculated by the LMTO-ASA method within the framework of the local-spin-density approximation, and the effect of X atoms on the magnetic properties were investigated. The magnetic moments of the Fe(4e) atoms which are nearest to the X atoms decrease. This is due to the hybridization between Fe(4e) d states and X valence states. On the other hand, the Fe(4d) atoms farthest from X atoms carry a very large magnetic moment. The Fe(4d) moment is indirectly influenced by X atoms through the neighbouring Fe and the enhancement increases for X=B, C and N, in that order. The hyperfine fields at Fe(4e) and Fe(8h) in Fe16N2 are nearly equal, though their magnetic moments are different. This fact can be explained on the basis of the difference of the contributions from the valence s electrons.

Theoretical predicts of half-metallic compounds with the C1b structure

Abstract The purpose of this study is to predict theoretically new half-metallic compounds. Changing lattice constants and atomic configurations and replacing constituent atoms in the C1b structure, we calculated the electronic structures and found the possibility for some compounds to be half-metallic; TMnSb (T  Rh, Pd, Ir, Pt) under pressure, TMnSb1 − xTex for a certain region of x and CoMZ (M  V, Ti; Z  Sn, Sb) in a special atomic configuration.

Electronic structures and improvement of magnetic properties of RFe12X (R = Y, Ce, Gd; X = N, C)

Abstract Electronic structures of RFe 12 and RFe 12 X (R = Y, Ce, Gd; X = N, C) were calculated to examine the effect of the X atoms on the magnetic properties. The formation of the bonding and antibonding states between the valence states of the X and Fe atoms produces the characteristic change in the density of state of the Fe atom. From this change, we can understand how the magnetic moments are changed by X atoms and that the spin fluctuation is restrained and the Curie temperature is enhanced by the introduction of X atoms.

Effects of N and Mo atoms on the magnetic properties of YFe12−xMox and YFe12−xMoxN

The electronic structures of YFe12−xMox and their nitrides were calculated to examine the effect of N and Mo atoms on the magnetic properties. The introduction of nitrogen produces favourable effects, while the substitution of Fe atoms by Mo atoms produces detrimental effects. These effects are examined by the dependence of the magnetic properties on the concentration and the atomic site of the Mo atoms.

Effects on electronic structures of atomic configurations in ternary compounds NiMZ (M Sc, Ti, Zr, Hf; Z Sn, Sb)

Abstract It will be shown from electronic structures of ternary compounds NiMZ that some of them are able to be a conductor or two types of semiconductors in the different atomic configurations and that the energy gaps determined by experiments come from the configuration where Ni and M atoms are separated.

Magnetic properties and electronic structures of CrMZ (M Fe, Co, Ni; Z P, As)

Abstract Electronic structures of the compounds CrMZ (M  Fe, Co, Ni, Z  P, As) were calculated to examine the magnetic properties. From the density of state for a nonmagnetic state, we can guess that Cr in CrMZ carries a magnetic moment but the M atom does not even though pure metals of Fe, Co and Ni are ferromagnets. It will also be shown that although the M atom is nonmagnetic, the magnetism of CrMZ changes with the M atom because the hybridization between the d states of the Cr and M atom affects the Cr d bands. These are confirmed by the total energies and electronic structures for the ferro- and antiferromagnetic states.