Electronic structure and magnetism ofFe3−xVxX

Arun Bansil

¹

,

S. Kaprzyk

²

,

P.E. Mijnarends

³

et al.

Abstract

We present first principles charge-and spin-selfconsistent electronic structure computations on the Heusler-type disordered alloys Fe 3−x V x X for three different metalloids X= (Si, Ga and Al). In these calculations we use the methodology based on the Korringa-Kohn-Rostoker formalism and the coherent-potential approximation (KKR-CPA), generalized to treat disorder in multi-component complex alloys. Exchange correlation effects are incorporated within the local spin density (LSD) approximation. Total energy calculations for Fe 3−x V x Si show that V substitutes preferentially on the Fe(B) site, not on the Fe(A,C) site, in agreement with experiment. Furthermore, calculations have been carried out for Fe 3−x V x X alloys (with, x = 0.25, 0.50 and 0.75), together with the end compounds Fe 3 X and Fe 2 VX, and the limiting cases of a single V impurity in Fe 3 X and a single Fe(B) impurity in Fe 2 VX. We delineate clearly how the electronic states and magnetic moments at various sites in Fe 3−x V x X evolve as a function of the V content and the 1 metalloid valence. Notably, the spectrum of Fe 3−x V x X (X=Al and Ga) develops a pseudo-gap for the majority as well as minority spin states around the Fermi energy in the V-rich regime which, together with local moments of Fe(B) impurities, may play a role in the anomalous behavior of the transport properties. The total magnetic moment in Fe 3−x V x Si is found to decrease non-linearly, and the Fe(B) moment to increase with increasing x; this is in contrast to expectations of the 'local environment' model, which holds that the total moment should vary linearly while the Fe(B) moment should remain constant. The common-band model which describes the formation of bonding and antibonding states with different weights on the different atoms, however, provides insight into the electronic structure of this class of compounds.

Failure oft−Jmodels in describing doping evolution of spectral weight in x-ray scattering, optical, and photoemission spectra of cuprates

“…1 and 2 are based on the QP-GW model 16,29 , an extension of our earlier Hartree-Fock (HF) model of AFM gap collapse 5,6,31,32 to the intermediate coupling regime by introducing a GWlike self-energy correction. [33][34][35][36] The self-energy in QP-GW model is dominated by a broad peak in Σ ′′ which produces the 'waterfall' effect 17,18 in the electronic dispersion by redistributing spectral weight into the coherent in-gap states and an incoherent residue of the undressed UHB and LHB. With underdoping, the in-gap states develop a pseudogap which we model as a (π, π)-ordered spin density wave.…”

Effect of the tetragonal distortion on the electronic structure, phonons and superconductivity in the Mo3Sb7 superconductor

“…[27] The crystal potential was constructed in the framework of the local density approximation (LDA), using von Barth and Hedin formula [28] for the exchangecorrelation part. For all atoms angular momentum cut- …”

Antiferromagnetic phase of the gapless semiconductorV3Al

“…Although the superconducting properties of V 3 Al in the A15 structure have been known for several decades, [10][11][12][13] when synthesized in the pseudo-Heusler D0 3 structure V 3 Al is expected to be an AF gapless semiconductor. [2,6,7] The D0 3 structure has the same space group as the L2 1 structure, but the binary D0 3 structure has a X 3 Z basis, while the ternary L2 1 structure has a X 2 YZ basis.…”

“…Figure 1(c) illustrates the D0 3 structure of V 3 Al where the Al atom occupies the 4a Wyckoff position at (0,0,0), the V atom labeled V1 occupies the 4b position at (1/2, 1/2, 1/2), and the remaining two V atoms labeled V2 occupy the 8c position at (1/4, 1/4, 1/4). [11] The atoms along the cubic body diagonal have an Al-V2-V1-V2-Al configuration. The local environment of V1 includes eight V2 nearest-neighbors and six Al second-nearest-neighbors, whereas the V2 atoms have four Al and four V1 nearest-neighbors and six V2 second-nearest-neighbors.…”