Coherent potential approximation

About: Coherent potential approximation is a research topic. Over the lifetime, 1930 publications have been published within this topic receiving 36805 citations.

CPA theory of diluted Heisenberg antiferromagnet with random first- and second-neighbour exchange bonds

Abstract: A coherent potential approximation (CPA) ansatz for a Heisenberg ferromagnet which possesses both nearest and next-nearest neighbour exchange interactions, is given. Spatial randomness caused by introduction of non-magnetic impurities, i.e. magnetic site dilution, is treated in the approximation where the bonds are taken to be independent. The occurrence of exchange bond fluctuations between pairs of magnetic atoms, is also considered. Numerical results are given for the coherent exchange integrals, spin-wave stiffness and the Curie temperature (which is derived within a random phase type of approximation) for a variety of situations.

Temperature-dependent resistivity and anomalous Hall effect in NiMnSb from first principles

Abstract: We present implementation of the alloy analogy model within fully relativistic density-functional theory with the coherent potential approximation for a treatment of nonzero temperatures. We calculate contributions of phonons and magnetic and chemical disorder to the temperature-dependent resistivity, anomalous Hall conductivity (AHC), and spin-resolved conductivity in ferromagnetic half-Heusler NiMnSb. Our electrical transport calculations with combined scattering effects agree well with experimental literature for Ni-rich NiMnSb with 1--2% Ni impurities on Mn sublattice. The calculated AHC is dominated by the Fermi surface term in the Kubo-Bastin formula. Moreover, the AHC as a function of longitudinal conductivity consists of two linear parts in the Ni-rich alloy, while it is nonmonotonic for Mn impurities. We obtain the spin polarization of the electrical current $Pg90%$ at room temperature and we show that $P$ may be tuned by chemical composition. The presented results demonstrate the applicability of an efficient first-principles scheme to calculate temperature dependence of linear transport coefficients in multisublattice bulk magnetic alloys.

First-principles study of spin-disorder resistivity of heavy rare-earth metals: Gd-Tm series

Abstract: Electrical resistivity of heavy rare-earth metals has a dominant contribution from thermal spin-disorder scattering. Here this spin-disorder resistivity is calculated for the Gd-Tm series of metals in the paramagnetic state. Calculations are performed within the tight-binding linear muffin-tin orbital method using two complementary methods: (1) averaging of the Landauer-B¨ uttiker conductance of a supercell over random noncollinear spin-disorder configurations, and (2) linear response calculations with the spin-disordered state described in the coherent potential approximation. The agreement between these two methods is found to be excellent. The spin-disorder resistivity in the series follows an almost universal dependence on the exchange splitting. While the crystallographic anisotropy of the spin-disorder resistivity agrees well with experiment, its magnitude is significantly underestimated. These results suggest that the classical picture of slowly rotating self-consistent local moments is inadequate for rare-earth metals. A simple quantum correction improves agreement with experiment but does not fully account for the discrepancy, suggesting that more complicated scattering mechanisms may be important.