Temperature dependent electronic transport in concentrated solid solutions of the 3d -transition metals Ni, Fe, Co and Cr from first principles

Abstract

An approach previously developed for the calculation of transport coefficients via the Mott relations is applied to the calculation of finite temperature transport properties of disordered alloys---electrical resistivity and the electronic part of thermal conductivity. The coherent-potential approximation is used to treat chemical disorder as well as other sources of electron scattering, i.e., temperature induced magnetic moment fluctuations and lattice vibrations via the alloy analogy model. This approach, which treats all forms of disorder on an equal first-principles footing, is applied to the calculation of transport properties of a series of fcc concentrated solid solutions of the $3d$-transition metals Ni, Fe, Co, and Cr. For the nonmagnetic alloys ${\mathrm{Ni}}_{0.8}{\mathrm{Cr}}_{0.2}$ and ${\mathrm{Ni}}_{0.33}{\mathrm{Co}}_{0.33}{\mathrm{Cr}}_{0.3}$, the combined effects of chemical disorder and electron-lattice vibrations scattering result in a monotonic increase in the resistivity as a function of temperature from an already large, $T=0$, residual resistivity. For magnetic ${\mathrm{Ni}}_{0.5}{\mathrm{Co}}_{0.5},{\mathrm{Ni}}_{0.5}{\mathrm{Fe}}_{0.5}$, and ${\mathrm{Ni}}_{0.33}{\mathrm{Fe}}_{0.33}{\mathrm{Co}}_{0.33}$, the residual resistivity of which is small, additional electron scattering from temperature induced magnetic moment fluctuations results in a further rapid increase of the resistivity as a function of temperature. The electronic part of the thermal conductivity in nonmagnetic ${\mathrm{Ni}}_{0.8}{\mathrm{Cr}}_{0.2}$ and ${\mathrm{Ni}}_{0.33}{\mathrm{Co}}_{0.33}{\mathrm{Cr}}_{0.33}$ monotonically increases with temperature. This behavior is a result of the competition between a reduction in the conductivity due to electron-lattice vibrations scattering and temperature induced increase in the number of carriers. In the magnetic alloys, electron scattering from magnetic fluctuations leads to an initial rapid decrease in thermal conductivity until this is overcome by an increasing number of carriers at temperatures slightly below the Curie temperature. Similar to the resistivity above ${T}_{C}$, the electronic parts of the thermal conductivities are close to each other in all alloys studied.