Showing papers on "Half-metal published in 2011"

Tunnel magnetoresistance effect and magnetic damping in half-metallic Heusler alloys

Abstract: Some full-Heusler alloys, such as Co(2)MnSi and Co(2)MnGe, are expected to be half-metallic ferromagnetic material, which has complete spin polarization. They are the most promising materials for realizing half-metallicity at room temperature owing to their high Curie temperature. We demonstrate a huge tunnel magnetoresistance effect in a magnetic tunnel junction using a Co(2)MnSi Heusler alloy electrode. This result proves high spin polarization of the Heusler alloy. We also demonstrate a small magnetic damping constant in Co(2)FeAl epitaxial film. The very high spin polarization and small magnetic constant of Heusler alloys will be a great advantage for future spintronic device applications.

Half-metallicity and magnetic properties of half-Heusler type Mn2Sn: Ab initio predictions

Abstract: Ab initio calculation have been carried out to investigate the electronic structure and magnetism of the compound Mn2Sn with the bcc half-Heusler structure. For the equilibrium lattice parameter 5.69 angstrom, Mn2Sn is predicted to be a half-metallic fully compensated ferrimagnet (also called half-metallic antiferromagnet) with zero total spin moment. This zero moment agrees well the Slatter-Pauling curve and mainly comes from the compensated Mn (A) and Mn (B) spin moments in antiparallel configuration. The half-metallicity of Mn2Sn is stable in a wide lattice-parameter range from 5.6 angstrom to 5.9 angstrom. Upon contraction of the lattice, a transition from half-metallicity to semimetallicity is observed. (C) Elsevier B.V. All rights reserved.

Magnetic surface states in high polarization materials

Abstract: Surfaces are often different materials, and typically have a different electronic structure from the bulk and since the dawn of surface science, surface-localized electronic states, surface states, have been extensively studied and investigated with growing accuracy. Of particular importance to spintronics are magnetic surface states. Interfaces will play a very important role in many spintronics devices, yet the interface properties are often ignored, poorly understood or badly characterized. For many nominally half metal materials, materials that in some ground state calculations exhibit 100% spin polarization, the magnetic surface states may significantly reduce the effective spin polarization. We review the magnetic surface states of several well known and often highly touted high spin polarized materials such as NiMnSb, Fe 3 O 4 , CoS 2 and CrO 2 . Finally, we summarize surface state measurements of magnetoelectric antiferromagnets Cr 2 O 3 , which has electrically controllable net surface spins, a major complication to the study of CrO 2 by photoemission.

Robust Half-Metallicity in a Chromium-Substituted AlN

Abstract: We investigate half metallicity in a chromium (Cr)-substituted AlN dilute magnetic semiconductor using the full-potential linearized augmented plane-wave method. Our results show that Al0.75Cr0.25N is half metal and holds a net integer magnetic moment of 3μβ with lattice compression. The half-metallic nature is maintained from the relaxed lattice constant 4.36 A to 4.09 A. An abrupt change of the physical properties is observed at a robust transition lattice constant of 4.09 A, and the material transforms from half metal to metal. We find that up to 6% compression, the material maintains its half-metallic nature. Furthermore, we also confirm that the origin of ferromagnetism in Al0.75Cr0.25N is double exchange.

ELECTRON DOPING EFFECTS ON ELECTRONIC AND MAGNETIC PROPERTIES IN Sr2FeReO6

Abstract: We have investigated the electronic and magnetic properties of electron-doped Sr2-xLaxFeReO6 (x = 0.0, 0.25, 0.5) using first-principles density functional theory within the generalized gradient approximation (GGA) and GGA + U schemes. Our results reveal that the symmetry of the La-doped compounds is decreased from tetragonal I4/m for perfect sample to monoclinic P21/n. With increasing La content the absolute magnetic moment of the Re site increases distinctly and the doped electrons are considered to occupy mainly the down-spin Re 5d band from the band calculation. Electronic doping is found to enhance the Curie temperature (Tc) and stabilize the ferromagnetic half-metallic ground states of Sr2FeReO6. And it is found that the increase of Tc is mainly caused by the increase of ferromagnetic interaction between the Fe–O–Fe.

The Electronic and Magnetic Properties of Half-metal Type MnFexCo2−xSi (with x = 0, 0.25, 0.5, 0.75 ,1, 1.25, 1.5, 1.75, and 2) Alloys

Abstract: The electronic and magnetic properties of MnFexCo2−xSi alloys have been calculated using density functional theory by Wien2k package, and a ferromagnetic ground state structure has been found for these alloys. The half-metallicity of the MnFe0.25Co1.75Si and MnFe1.75Co0.25Si is discussed in the light of changes in the orbital hybridization as a result of Fe and Co doping in MnCo2Si and MnFe2Si, respectively. The calculated magnetic moment of MnFexCo2−xSi alloys shows that the effect of Si atom on magnetic properties of these compounds is negligible compared to Mn, Fe, and Co atoms. The variation of magnetic moment versus x has been investigated. By fitting the nonlinear variation of the calculated magnetic moment versus concentration with third- order polynomials, the magnetic moment bowing factor has been calculated.

Electronic Structure and Spin-Injection of Co-Based Heusler Alloy/ Semiconductor Junctions

Abstract: The electronic structures of Co-based Heusler alloys with nonstoichiometric atomic compositions as well as those at the interface of semiconductor junctions are investigated using first principles band calculations. It is shown that the electronic structure of a Co-based Heusler alloy is half-metallic, even for nonstoichiometric but Co-rich compositions, whereas the half-metallicity is lost for Co-poor compositions. It is also shown that magnetic moments at the interface of Co2MnSi/ Si junctions are sensitive to the growth direction and interface structure of the junctions. Efficient spin-injection into Si can be achieved by using a (111)-oriented Co-rich Heusler alloy and controlling the layer-by-layer stacking sequence at the interface.