First-Principles Calculation and Experimental Investigations on Full-Heusler Alloy Co $_{2}$ FeGe
22 Sep 2009-IEEE Transactions on Magnetics (Institute of Electrical and Electronics Engineers)-Vol. 45, Iss: 10, pp 3997-3999
TL;DR: In this paper, first principles for the full Heusler alloy Co2FeGe within the scheme of density functional theory using plane-wave self-consistent field method were carried out.
Abstract: First-principles calculation has been carried out for the full Heusler alloy Co2FeGe within the scheme of density functional theory using plane-wave self-consistent field method. The spin polarized band structure does not show any energy gap at the Fermi level for both up and down spin electrons. Atom resolved magnetic moment on each site was observed to be 1.3 muB (Co), 2.9 muB (Fe), and 0.0 muB (Ge). X-ray diffraction studies reveal a B2-type structure for the bulk sample and cubic L21 structure for the melt-spun ribbons. The lattice parameter value for the ribbon is 5.736 Aring, and its Curie temperature is around 981 K. The magnetic moment per formula unit at 5 K was observed to be 5.74 muB. The low temperature data ( < 100 K) follows the relationrho = rho0 + AT2 + BT4.5 , indicating the presence of one magnon spin-flip scattering.
Citations
More filters
TL;DR: The spin polarization of ferromagnetic Heusler alloys, Co 2 Fe(Ga x Ge 1−x ) ( x ǫ = 0, 0.75, and 1), is investigated by point contact Andreev reflection (PCAR) measurements as discussed by the authors.
105 citations
TL;DR: Using a newly developed highly spin-polarized Heusler alloy, Co2Fe(Ga05Ge05) (CFGG), as ferromagnetic layers, a current-perpendicular-to-plane pseudospin valve with large resistance change-area product (ΔRA) of 95mΩμm2 and magnetoresistance (MR) ratio (100×ΔR/R) of 417% at 300 K were fabricated in this paper.
Abstract: Using a newly developed highly spin-polarized Heusler alloy, Co2Fe(Ga05Ge05) (CFGG), as ferromagnetic layers, we have fabricated a current-perpendicular-to-plane pseudospin valve with large resistance change-area product (ΔRA) of 95 mΩ μm2 and magnetoresistance (MR) ratio (100×ΔR/R) of 417% at 300 K These values were further enhanced to ΔRA=264 mΩ μm2 and MR=1291% at 10 K The large MR values are attributed to the high spin polarization of the CFGG alloy confirmed by point contact Andreev reflection measurements
98 citations
TL;DR: In this article, structural, magnetic and electronic properties of stoichiometric Co2 YZ Heusler alloys have been studied by means of ab initio calculations and Monte Carlo simulations.
Abstract: Structural, magnetic and electronic properties of stoichiometric Co2 YZ Heusler alloys (Y = Cr, Fe, Mn and Z = Al, Si, Ge) have been studied by means of ab initio calculations and Monte Carlo simulations. The investigations were performed in dependence on different levels of approximations in DFT (FP and ASA modes, as well as GGA and GGA + U schemes) and external pressure. It is shown that in the case of the GGA scheme the half-metallic behavior is clearly observed for compounds containing Cr and Mn transition metals, while Co2FeZ alloys demonstrate the pseudo half-metallic behavior. It is demonstrated that an applied pressure and an account of Coulomb repulsion (U) lead to the stabilization of the half-metallic nature for Co2 YZ alloys. The strongest ferromagnetic inter-sublattice (Co–Y) interactions together with intra-sublattice (Co–Co and Y–Y) interactions explain the high values of the Curie temperature obtained by Monte Carlo simulations using the Heisenberg model. It is observed that a decrease in valence electrons of Y atoms (i.e. Fe substitution by Mn and Cr) leads to the weakening of the exchange interactions and to the reduction of the Curie temperature. Besides, in the case of the FP mode Curie temperatures were found in a good agreement with available experimental and theoretical data, where the latter were obtained by applying the empirical relation between the Curie temperature and the total magnetic moment.
43 citations
TL;DR: In this paper, the optical properties of a half-metallic full-Heusler Co2FeGe alloy were investigated experimentally and theoretically, and first principles calculations of the electronic structure and the dielectric tensor were performed using the fullpotential linearized-augmented-plane-wave method.
Abstract: Optical properties of ferromagnetic half-metallic full-Heusler Co2FeGe alloy are investigated experimentally and theoretically. Co2FeGe thin films were obtained by DC magnetron sputtering and show the saturation magnetization at T = 10 K of m≈5.6μB/f.u., close to the value predicted by the Slater-Pauling rule. First-principles calculations of the electronic structure and the dielectric tensor are performed using the full-potential linearized-augmented-plane-wave method in the generalized gradient approximation (GGA) and GGA + U approximation. The measured interband optical conductivity spectrum for the alloy exhibits a strong absorption band in the 1–4 eV energy range with pronounced fine structure, which agrees well with the calculated half-metallic spectrum of the system, suggesting a near perfect spin-polarization in the material.
26 citations
TL;DR: In this paper, the optical properties of a half-metallic full-Heusler Co$2}$FeGe alloy were investigated experimentally and theoretically, and first-principles calculations of the electronic structure and the dielectric tensor were performed using the full-potential linearized-augmented-plane-wave method in the generalized gradient (GGA) and GGA+U approximations.
Abstract: Optical properties of ferromagnetic half-metallic full-Heusler Co$_{2}$FeGe alloy are investigated experimentally and theoretically. Co$_{2}$FeGe thin films were obtained by DC magnetron sputtering and show the saturation magnetization at $T$=10 K of $m\approx$5.6 $\mu_{B}$/f.u., close to the value predicted by the Slater-Pauling rule. First-principles calculations of the electronic structure and the dielectric tensor are performed using the full-potential linearized-augmented-plane-wave method in the generalized gradient (GGA) and GGA+U approximations. The measured interband optical conductivity spectrum for the alloy exhibits a strong absorption band in the 1 - 4 eV energy range with pronounced fine structure, which agrees well with the calculated half-metallic spectrum of the system, suggesting a near perfect spin-polarization in the material.
23 citations
References
More filters
TL;DR: In this article, the magneto-optical Kerr rotation in more than 200 metallic systems comprising alloys as well as intermetallic compounds of 3D transition metals was studied and the saturation moment at 4.2 K was determined.
686 citations
TL;DR: In this article, structural and magnetic investigations of the Heusler compound Co2FeSi have been carried out by means of x-ray magnetic circular dichroism and magnetometry, and it has been shown that this compound is, currently, the material with the highest magnetic moment (6μB) and Curie temperature (1100K) in the classes of half-metallic ferromagnets.
Abstract: This work reports on structural and magnetic investigations of the Heusler compound Co2FeSi. X-ray diffraction and Mosbauer spectrometry indicate an ordered L21 structure. Magnetic measurements by means of x-ray magnetic circular dichroism and magnetometry revealed that this compound is, currently, the material with the highest magnetic moment (6μB) and Curie temperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets.
374 citations
TL;DR: In this paper, the lattice constants of these compounds were determined and the formation of the Heusler L 2 1 -type phase was compared with model predictions, and it was found that only a limited number of these combinations leads to the cubic L2 1 -Heusler-type compounds.
359 citations
TL;DR: In this article, structural and magnetic investigations of the Heusler compound Co$_2$FeSi were carried out using X-ray diffraction and M *ss bauer spectrometry.
Abstract: This work reports on structural and magnetic investigations of the Heusler compound Co$_2$FeSi. X-Ray diffraction and M\"o\ss bauer spectrometry indicate an ordered $L2_1$ structure. Magnetic measurements by means of X-ray magnetic circular dichroism and magnetometry revealed that this compound is, currently, the material with the highest magnetic moment ($6 \mu_B$) and Curie-temperature (1100K) in the classes of Heusler compounds as well as half-metallic ferromagnets.
337 citations
TL;DR: In this paper, it was shown that the magnetic moment of half-metallic ferromagnets can be calculated from the generalized Slater-Pauling rule, and empirically that the Curie temperature of Co2-based Heusler compounds can be estimated from a seemingly linear dependence on the magnetic moments.
Abstract: A concept is presented serving to guide in the search for materials with high spin polarization. It is shown that the magnetic moment of half-metallic ferromagnets can be calculated from the generalized Slater-Pauling rule. Furthermore, it was found empirically that the Curie temperature of Co2-based Heusler compounds can be estimated from a seemingly linear dependence on the magnetic moment. As a successful application of these simple rules, it was found that Co2FeSi is, actually, the half-metallic ferromagnet exhibiting the highest magnetic moment and the highest Curie temperature measured for a Heusler compound.
223 citations