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.

First-principles material design and perspective on semiconductor spintronics materials

Abstract: We investigate the electronic structure and magnetic properties of III–V compound semiconductor based dilute magnetic semiconductors (DMS) from first-principles. The electronic structure of DMS is calculated by using the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA) method in connection with the local density approximation (LDA). Describing the magnetic properties by a classical Heisenberg model, effective exchange interactions are calculated by applying magnetic force theorem for two impurities embedded in the CPA medium. With the calculated exchange interactions, TC is estimated by using the mean field approximation, the random phase approximation and the Monte Carlo simulation. In the above compounds, the magnetic interactions are well described from double exchange picture. Due to the short-range interactions, high-TC is difficult to achieve in the presently investigated materials. Based on the present results, two strategies towards high-TC are proposed to realize useful DMS materials. One uses spinodal decomposition to realize high blocking temperature in super-paramagnetic blocking phenomena and the other uses co-doping method to realize high concentration doping of magnetic impurities for high-TC.

Effective one-band hamiltonian for cuprate superconductor metal-insulator transition

Abstract: Starting from the three-band Hubbard hamiltonian H and projecting out of the Hilbert space a group of high-energy states, we obtain an effective one-band model Heff. Heff has a form similar to the Hubbard model, but the hopping terms depend on occupation numbers. We give analytical, accurate enough expressions relating the parameters of Heff to those of H. Treating Heff in an approximation similar to Hubbard III the problem is reduced to an alloy with diagonal and off-diagonal disorder. Using the criterion of the closing of the gap in this effective alloy for the metal-insulator transition, we obtain a metal-insulator phase diagram for the undoped system as a function of the parameters of H. The system is insulating for realistic parameters.

Optical properties of diluted magnetic semiconductors in coherent potential approximation

Abstract: We study optical properties of a single band model for (III,Mn)V diluted magnetic semiconductors (DMS), treating the impurity spins fully quantum mechanically in the coherent potential approximation (CPA) Our CPA results show an interesting dependence of the optical conductivity on Kondo coupling, carrier density, nonmagnetic potential, and temperature We find that by taking into account the spin–flip effect, the calculated conductivity is in reasonable agreement with the ones obtained by Monte-Carlo simulations and experiments

On the orientational dependence of giant magnetoresistance

Abstract: The functional dependence of the giant magnetoresistance (GMR) with respect to the relative angle between the orientations of the magnetization in the magnetic slabs of a trilayer system is calculated by using the Kubo-Greenwood formula for electrical transport together with the fully-relativistic spin- polarized screened Korringa-Kohn-Rostoker method for semi-innite systems and the coherent potential approximation. It is found that the functional dependence of the GMR is essentially of the form (1 cos').