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.

Excitations in the Heisenberg antiferromagnet at finite temperature using coherent potential approximation

Abstract: In a previous paper the dynamical properties of the S=2/1 Heisenberg ferromagnet were discussed using an extension of the RPA. This theory is extended to theS=2/1 Heisenberg antiferromagnet. The method consists of representing the effect of temperature by a fixed array of up and down spins. The spin-wave excitations are calculated in this disordered array using the coherent potential approximation for a system of potentials due to the appropriate distribution of bonds. A relation between the number of reversed spins and temperature is derived from self-consistency and the transition temperature TN is found to be the same as the RPA result. The method gives a reasonable approximation overall to the spin-wave response at T

The ground state phase diagram of the diluted ferromagnetic Kondo-lattice model

Abstract: We investigate the existence of several (anti-)ferromagnetic phases in the diluted ferromagnetic Kondo-lattice model, i.e. ferromagnetic coupling of local moment and electron spin. To do this we use a coherent potential approximation (CPA) with a dynamical alloy analogy. For the CPA we need effective potentials, which we obtain first from a mean-field approximation. To improve this treatment we use in the next step a more appropriate moment conserving decoupling approach and compare the two methods. The different magnetic phases are modeled by defining two magnetic sub-lattices. As a result we present zero-temperature phase diagrams according to the important model parameters and different dilutions.

Quantum spins in the double exchange model of manganites

Abstract: In the simplest double exchange model of manganites local spins S associated with Mn ions interact with electrons in the conduction band via strong ferromagnetic Hund's rule coupling. A many-body coherent potential approximation (CPA) is developed which reproduces the exact atomic limit of the model, for all S and arbitrary filling of the band, and which reduces to an earlier one-electron CPA in the low density limit. The electronic structure and resistivity are calculated in the paramagnetic state and it is found that the resistivity arising from spin scattering is far too small to explain the large values observed in the neighbourhood of the Curie temperature. Magnetic states are most easily investigated for S= 1 2 and it appears that the many-body CPA does not give a transition to ferromagnetism in this case.

Magnetic form factor and spin-density asphericity of Ni-Cu.

Abstract: Magnetic form-factor measurements were made on single crystals of a Ni-Cu alloy containing 47.6 at. % Cu. The results give a magnetic moment of 0.088 ..mu beta../atom at T = 4.2 K and H = 40 kOe in excellent agreement with bulk magnetization data. Despite this order of magnitude decrease in moment relative to Ni, the form factor is the same in both the radial distribution and the asphericity as that previously observed for pure Ni. This result is in strong contrast with an early coherent potential approximation calculation which yields a continuous variation of ..gamma.., the fractional E/sub g/ population, with Cu content. It is suggested that some of this discrepancy may be attributed to the neglect of local environment effects, which are known to be important for the magnetism of Ni-Cu alloys.

Application of the narrow band model for disorders ferromagnetic alloys to the solid solutions Fe1−xCoxS2 and Ni1−xCoxS2

Abstract: The narrow band model of Hubbard, generalized for random disordered alloys, is used to discuss the ferromagnetism in the pyrite solid solutions Fe1−xCoxS2 and Ni1−xCoxS2. This discussion is made within the coherent potential approximation for treating disorder.