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.

RPA-CPA theory for magnetism in disordered Heisenberg binary systems with long-range exchange integrals

Abstract: We present a theory based on Green's-function formalism to study magnetism in disordered Heisenberg systems with long-range exchange integrals. Disordered Green's functions are decoupled within the Tyablicov scheme and solved with a coherent potential approximation (CPA) method. The CPA method is the extension of Blackmann-Esterling-Beck approach to systems with an environmental disorder term which uses cumulant summation of the single-site noncrossing diagrams. The crucial point is that we are able to treat simultaneously and self-consistently the random-phase approximation (RPA) and CPA loops. It is shown that the summation of the s-scattering contribution can always be performed analytically, while the p,d,f... contributions are difficult to handle in the case of long-range coupling. To overcome this difficulty we propose and provide a test of a simplified treatment of these terms. In the case of the three-dimensional disordered nearest-neighbor Heisenberg system, a good agreement between the simplified treatment and the full calculation is achieved. Our theory allows us in particular to calculate the Curie temperature, the spectral functions, and the temperature dependence of the magnetization of each constituent as a function of concentration of impurity. Additionally it is shown that a virtual crystal treatment fails even at low impurity concentration.

Enhanced Electronic and Magnetic Properties of Cr- and Mn-Doped GeC Zinc Blende

Abstract: The electronic and magnetic properties of the doped GeC by Cr and Mn are studied using the Koringa-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA). We have determined the nature of the forbidden band gap and investigated the metallic character when the doping is made by the chromium and the manganese. On the other hand, although the doping is above the percolation threshold, the total magnetic moment for Ge1 − 0.25TM0.25C is 0.491 and 0.67 μB for Cr and Mn, respectively. Besides, the polarization as well as the main responsible source of magnetism in the system is determined. Finally, using the mean field theory, the Curie temperature TC is estimated for different concentrations. It was found that the effect of doping with Mn had a significant impact on TC since it exceeded the room temperature. The findings of this work suggest GeC-based diluted magnetic semiconductors as potential materials for electronics applications.