HALF-METALLICITY OF BULK AND (001) SURFACE IN THE Co2FeGa HEUSLER COMPOUND:A THEORETICAL STUDY

We analyze the electronic and magnetic characteristics of the Co2FeGa Heusler compound and the surface (001) Co2FeGa with the [Formula: see text] structure based on first principles calculations. The Co2FeGa Heusler possesses high Curie temperatures and magnetization, and is therefore the most studied composition for spintronics applications. We examine the influences of (001) surface and relate interactions on the half-metallicity and the magnetic properties with two ideal terminations named Co–Co and Fe–Ga and modified Co– terminated (001) surfaces. We notice that the half-metallicity seen in the bulk Co2FeGa is destroyed at all terminations, the spin polarization is smaller than that the bulk, the values of the Co–Co, Fe–Ga and Co– terminations are 50%, 27% and 43% respectively, but all surfaces are shown to be metallic due to the surface states staying at the Fermi level despite the confirmed [Formula: see text] band splitting caused by the liaison influence. The calculated magnetic moment of these terminations was found for all the subsurface to be close to that of the bulk system and this makes this compound of maximum benefit in the pilot applications of spintronic systems.

Theoretical Studies on the Magnetic Moments of Iron Nitrides Including Fe16N2

ABSTRACTThe spin-polarized band calculations for the iron nitrides, Fe3N, Fe4N and Fe16N2, have been performed with use of LMTO-ASA Method in the frame of local spin density functional formalism. The results show that the most distant Fe atoms from N have the largest magnetic moment. The central role of the N atom is to bring about the large magnetic moments through the lattice expansion. Concurrently, the N atoms promote an itinerancy of electrons and then in turn prevent the exchange-splitting. This results in an Fe16N2 with the lowest N concentration having the largest magnetic moments. Quantitatively, the obtained magnetic moments are in fair agreements with the experimental results except for Fe16Nr The calculated magnetic moment of Fe6N2 is about 2.4 ΜB/Pε, while the measured value is reported as 3.5 ΜB/FB. The orbital magnetic moment of Fe16N2 is about 0.07 ΜB, which is too small to make up for the difference from the experimental value.

ELECTRONIC STRUCTURE OF THE PEROVSKITE OXIDES SrCrO3 AND PbCrO3

The electronic structure calculations of the perovskite oxides SrCrO 3 and PbCrO 3 performed both in the paramagnetic and antiferromagnetic phases are reported here. The calculations were carried out using the Linear Muffin Tin Orbital method within the Atomic Sphere Approximation. The quantitative results obtained are found to give a good description of the electronic states of SrCrO 3 and are in agreement with the Goodenough’s qualitative chemical picture. However, it is not able to predict the semiconducting gap in PbCrO 3 which is an antiferromagnetic semiconductor. But the value of the theoretically calculated magnetic moment at the Cr site in PbCrO 3 is found to be in good agreement with the experimentally observed value. The calculations show strong hybridisation between the Cr -3d and O -2p orbitals and the density of states at the Fermi energy has major contributions from these hybridised orbitals.