First-Principles Calculation of Transport Properties of Heusler Alloy Co2MnAl at Finite Temperatures

We develop a framework for first-principles calculations of the transport properties of magnetic materials at finite temperatures within the coherent potential approximation. First, we calculate the grand potential by the tight-binding linearized muffin-tin orbital method and apply it to the Kubo formula to obtain the temperature dependence of the conductivities. Next, we demonstrate the computation for the magnetic moments M(T), longitudinal and transverse electrical conductivities, sigma(xx)(T), sigma(xy)(1), Seebeck coefficients S-xx(1), and anomalous Nernst coefficients N-xy(1) of Co2MnAl of both L2(1) and B2 structures. It is found that sigma(xx)(1) of L2(1) and B2 structures exhibit slow relaxation with temperature compared with most transition metal alloys, which reflects a transition of the system from a half-metallic to metallic system with increasing temperature. The sigma(xy)(T = 0) of the B2 structure is much smaller than that of the L2(1) structure, while S-xx(T) of the B2 structure exhibits slower relaxation with temperature than the L2(1) structure. The S-xx(T) and N-xx(1) exhibit nonmonotonic variation in the low temperature region and the values above room temperature are in agreement with the experimental data.