Structural and magnetic phase transitions in Fe100 100–x xAl Alx x alloys: an alloys: an ab inito ab inito study

Abstract

The aim of the present work is a complex study of structural and magnetic phase transitions in  Fe100–x Alx(15 ≤ x ≤ 25 at.%) alloy with the help of density functional theory at zero temperature. In this work, using the Korringa – Kohn – Rostoker Greens function method with a coherent potential approximation of the equilibrium lattice parameters, ground-state energy, and magnetic exchange interactions for D03, B2 и A2 structures are calculated. The equilibrium 2 lattice constants demonstrate increasing behavior with increasing Al content. Studies of the ground-state energies show that the D03 structure is the most stable at all concentrations. Using the values of the equilibrium total energies of the system, the temperatures of structural phase transitions are estimated. With the help of mean-field approximation in the frame of the Heisenberg model, the Curie temperatures are obtained in a wide concentration range. Curie temperatures decrease with increasing of Al content. Based on structural and magnetic transition temperatures, the theoretical phase diagram of Fediagram Fe100–x Alx alloy was plotted. The phase diagram follows that the structural transitions from the ordered cubic phase to a completely disordered structure occur via a partially ordered structure over the entire concentration range with temperature increasing. The obtained phase diagram is in qualitative agreement with experimental data.