Computer Modeling of Magnetic Properties of Disordered BCC Phase of Fe100-xMex Alloys (Me = Al, Ga, Ge)

Abstract

In this paper, within the framework of density functional theory for the disordered phase A2 of Fe-Me alloys (Me = Al, Ga, Ge) the magnetic exchange constants Jij are calculated and the Curie temperatures TC are estimated in dependence of the concentration of Me = Al, Ga, Ge (in the range of 0 ≤ x ≤ 14 at. %) and the crystal lattice parameter (in the range of 2,7 ≤ a ≤ 3,0 Å). The Jij distribution obtained in the paper demonstrates non-linear behavior. The highest ferromagnetic interaction in the first coordination sphere is ≈23 meV. In the third coordination sphere, antiferromagnetic exchange interaction is observed, which reaches a value of ≈ –2,5 meV. Magnetic transition temperatures calculated using the mean field approximation based on the experimental values and the a0 parameters calculated within the density functional theory show the presence of a concentration range of 4 ≤ x ≤ 8 at. % in which TC increases. The cross-section of the calculated Curie temperature distribution shows that for all studied Fe-Me alloys with the lattice parameter a0 = 2,94 Å, it is possible to construct a dependence TC(x) that is in quality agreement with the experimental one.