A new diluted magnetic semiconductor: The half-metallic ferromagnet CoTi(1-x)FexSb

Half-Heusler compounds with 18 valence electrons are semi-conducting. It will be shown that doping with electrons results in half-metallic ferromagnets, similar to the case of diluted semi-conductors. CoTiSb is known to be a semi-conducting Half-Heusler compound. Doping by Fe is expected to result in ferromagnetic order. It was found that Ti can be replaced by up to about 10% Fe while its crystal structure still remains C1b, which was proved by X-ray powder diffraction. SQUID magnetometry revealed a magnetic moment of 0.32 mB per unit cell at 5K.Comment: JMMM accepte

The half-metallic ferromagnet Co2Mn0.5Fe0.5Si

Electronic structure calculation were used to predict a new material for spintronic applications. Co2Mn0.5Fe0.5Si is one example which is stable against on-site correlation and disorder effects due to the position of the Fermi energy in the middle of the minority band gap. Experimentally the sample were made exhibiting L21 structure and a high magnetic order.Comment: 5 pages, 2 Figures, J. Magn. Magn. Mater. accepte

Structural, magnetic, and transport properties of Co2_2FeSi Heusler films

We report the deposition of thin Co$_2$FeSi films by RF magnetron sputtering. Epitaxial (100)-oriented and L2$_1$ ordered growth is observed for films grown on MgO(100) substrates. (110)-oriented films on Al$_2$O$_3$(110) show several epitaxial domains in the film plane. Investigation of the magnetic properties reveals a saturation magnetization of 5.0 $mu_B/f.u.$ at low temperatures. The temperature dependence of the resistivity $rho_{xx}(T)$ exhibits a crossover from a T^3.5 law at T<50K to a T^1.65 behaviour at elevated temperatures. $rho_{xx}(H)$ shows a small anisotropic magnetoresistive effect. A weak dependence of the normal Hall effect on the external magnetic field indicates the compensation of electron and hole like contributions at the Fermi surface.Comment: 10 pages, 9 figures to be published in J. Phys. D: Appl. Phy

Electronic Structure, Localization and Spin-State Transition in Cu-substituted FeSe: Fe1−x_{1-x}Cux_xSe

We report density functional studies of the Fe$_{1-x}$Cu$_x$Se alloy done using supercell and coherent potential approximation methods. Magnetic behavior was investigated using the disordered local moment approach. We find that Cu occurs in a nominal $d^{10}$ configuration and is highly disruptive to the electronic structure of the Fe sheets. This would be consistent with a metal insulator transition due to Anderson localization. We further find a strong cross over from a weak moment itinerant system to a local moment magnet at $x \approx 0.12$. We associate this with the experimentally observed jump near this concentration. Our results are consistent with the characterization of this concentration dependent jump as a transition to a spin-glass