Influence of mixing the low-valent transition metal atoms (Y, Y[sup (original) (raw)
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Journal of Applied Physics, 2007
We complement our study on the doping and disorder in Co2MnZ compounds [I. Galanakis, K. Özdoğan, B. Aktaş, and E. Şaşıoğlu, Appl. Phys. Lett. 89, 042502 (2006) and K. Özdoğan, E. Şaşıoğlu, B. Aktaş, and I. Galanakis, Phys. Rev. B 74, 172412 (2006)] to cover also the quaternary Co2[Y1−xYx∗]Z compounds with the lower-valent transition metals Y, Y∗ being Cr, Mn, or Fe and the sp atom Z being one of Al, Ga, Si, Ge, and Sn. This study gives a global overview of the magnetic and electronic properties of these compounds since we vary both Y and Z elements. Our results suggest that for realistic applications the most appropriate compounds are the ones belonging to the families Co2[Mn1−xCrx]Z with x>0.5 irrespectively of the nature of the sp atoms since they combine high values of majority density of states at the Fermi level due to the presence of Cr, and half-metallicity with large band gaps. On the other hand, the presence of Fe considerably lowers the majority density of states at th...
2006
We complement our study on the doping and disorder in Co$_2$MnZ compounds [I. Galanakis \textit{et al.}, Appl. Phys. Lett. \textbf{89}, 042502 (2006) and K. \"Ozdo\~gan \textit{et al.}, Phys. Rev. B \textbf{74}, (2006)] to cover also the quaterarny Co$_2$[Y$_{1-x}$Y$^*_x$]Z compounds with the lower-valent transition metals Y,Y$^*$ being Cr, Mn or Fe and the sp atom Z being one of Al, Ga,
2014
Based on density functional theory (DFT) calculations, the electronic and magnetic properties of Co2YGe Heusler compounds (Y = Sc, Ti, V, Cr, Mn and Fe) were investigated. The density of states (DOS) and band structures were studied to understand their electronic properties. Of the investigated systems, Co2CrGe and Co2MnGe exhibited 100% spin polarisation at the EF. Co2CrGe was the most stable half-metallic ferromagnet (HMF) with a 0.24 eV energy gap at the Fermi level in the spin down channel. The total magnetic moment also increased as Y went from Sc to Fe, i.e., with increasing valence electrons. The calculated magnetic moments for Co2CrGe and Co2MnGe were 3.999 μB and 5.00 μB, respectively. Based on the calculated results, the HMF character was predicted for Co2CrGe and Co2MnGe.
Journal of Superconductivity and Novel Magnetism, 2016
The structural, electronic, and magnetic properties of the full-Heusler compounds Co 2 MnZ (Z = Al, Ge, Si, Ga) have been investigated using the first-principles calculations with the full-potential linear-augmented plane wave method within the density functional theory. The electronic structures and magnetic properties of the Co 2 MnZ (Z = Al, Ge, Si, Ga) compounds with both Hg 2 CuTi-and Cu 2 MnAl-type structures are studied. It is found that the calculated lattice constants are in good agreement with the theoretical values. Using the general gradient approximation, we observe that the Cu 2 MnAl-type structure is more stable than the Hg 2 CuTi type. The Co 2 MnZ (Z = Al, F.
Materials Today Communications, 2020
We study the structural, electronic, and magnetic properties of Co 2 ZAl compounds employing a pseudopotential electronic band structure method. The stability of the compounds is established through formation and cohesive energy calculations. The effect of the lattice parameter variation on the electronic and magnetic properties of the compounds is investigated and meticulous explanation is provided for the observed behavior. The variation of the individual spin magnetic moments and the stability of the total spin magnetic moment during the expansion and contraction of the lattice parameter is observed and an attempt is made to understand the obtained behavior. Finally, we implement DFT+U to examine its consequences on the electronic and magnetic properties of the Co 2 ZAl compounds. We find that the use of DFT+U is not justified for these compounds and in some cases like Co 2 MnAl it produces unrealistic properties. Exception is Co 2 FeAl where the desired half-metallicity is restored after the inclusion of on-site correlations. We explain why the on-site correlations might be important for Co 2 FeAl by comparing it with other Heusler alloys where the correlation was found to be meaningful to explain the observed magnetic moments.
We have calculated the electronic and magnetic properties of 3d transition metal based full Heusler compounds Co 2 CrZ (Z = Ga, Ge, As), by using full potential linearized augmented plane wave (FP-LAPW) method. The calculated density of states (DOS) and band structure for Co 2 CrZ shows the existence of band gap in their minority-spin channel. The respective energy gaps of Co 2 CrGe and Co 2 CrGa are 0.24 and 0.38 eV with their Fermi energies (E F s) lie exactly at the gap. The compound Co 2 CrAs when treated with local spin density approximation (LSDA) does not show half metallic ferromagnetism (HMF) even though there exist a gap this is because the E F does not lie at the middle of the gap. We have considered Co 2 CrAs as strongly correlated system as Cr-d states at E F are strongly localized thus the system was treated in terms of the LSDA + U. The total magnetic moment of Co 2 CrAs was found to be an exact integer value 5.00 l B within LSDA + U. We have also found that the total magnetic moments increase as the Z goes from Ga to As.
Physical Review Materials
In this paper we report an experimental study of structural, magnetic, and mechanical properties of quaternary Heusler alloys Co 2−x Y x FeSi (Y = Co, Fe, Mn, Cr, V, Ti, or Sc, 0 x 1) and the experimental findings are supported by ab initio electronic structure calculations. The alloys were synthesized using an arc-melting technique. Single phase microstructures are observed for all alloys substituted with low-valence transition metals Y except Sc. X-ray powder diffraction patterns at room temperature show the presence of Heusler-like face-centered cubic crystal structure in all single phase specimens. The low-temperature saturation magnetic moments, as determined from magnetization measurements, agree fairly well with our theoretical results and also follow the Slater-Pauling rule of thumb for half-metals, a prerequisite for half-metallicity. The alloys are predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations using the GGA+U approach. All stable compounds are observed to have high Curie temperatures with linear dependence with the valence electrons concentration in the alloys. Relatively high hardness values are also measured, approaching 15.7 GPa for Ti-substituted material, highest among the values reported for Heuslers so far. All these properties strongly suggest the alloys are promising for the spintronic applications at room temperature and above.