Abstract:
In this paper, the magnetic properties of the disordered A2 phase of Fe$_{100-x}$Ge$_x$ alloys were studied using methods of density functional theory. The distribution of the magnetic exchange interaction parameters $J_{ij}$ obtained in the study exhibits nonlinear behavior. The strongest ferromagnetic interaction in the first coordination sphere is $\sim$23.3 meV. In the third and fourth coordination spheres, an antiferromagnetic exchange interaction is observed, reaching a value of $\sim$-2.5 meV. The magnetic transition temperatures, calculated using the Mean-field approximation based on the experimental values of $a$ and the parameters $a_0$ calculated within the framework of density functional theory, indicate the presence of a concentration range of 4 $\le x\le$ 8 at.%, in which $T_C$ increases. The cross-section of the calculated Curie temperature distribution shows that for the studied Fe–Ge alloys with lattice parameters less than 2.74 A and greater than 2.94 A, it is possible to construct a dependence $T_C(x)$ that is in quality agreement with the experimental one.
Keywords:Fe–Ge alloys, density functional theory, exchange interaction, Curie temperature.
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