Magnetic properties of a disordered Heisenberg binary spin system with long-range exchange

TL;DR

This paper investigates how substitutional disorder and long-range exchange interactions, including RKKY, affect the magnetic properties of disordered Heisenberg binary spin systems, revealing significant impacts on magnetization and Curie temperature.

Contribution

It introduces a combined CPA and Tyablikov approximation approach to analyze long-range exchange effects in disordered magnetic systems, including RKKY interactions.

Findings

Long-range exchange significantly influences magnetization.

Curie temperature is affected by long-range interactions.

Disorder impacts magnetic properties differently with long-range exchange.

Abstract

The influence of substitutional disorder on the magnetic properties of disordered Heisenberg binary spin systems with long-range exchange integrals is studied. The equation of motion for the magnon Green's function which is decoupled by the Tyablikov approximation is solved in the Blackman-Esterling-Berk(BEB) coherent potential approximation(CPA) framework, where the environmental disorder term is treated by virtual crystal approximation. The long-range exchange integrals include a power-law decaying and an oscillating Ruderman-Kittel-Kasuya-Yosida(RKKY) exchange interaction. The resulting spectral density, which is calculated by CPA self-consistent equation, is then used to estimate the magnetization and Curie temperature. The results show, in the case of the three-dimensional simple cubic systems, a strong influence of ferromagnetic long-range exchange integrals on the magnetization and Curie temperature of the systems, which is obviously different from the calculation of short-range interaction.