Ab initio study of atomic ordering and spin-glass transition in dilute CuMn alloys

An archetypical spin-glass metallic alloy, Cu0.83Mn0.17, is studied by means of an ab initio based approach. First-principles calculations are employed to obtain effective chemical, strain-induced, and magnetic exchange interactions, as well as static atomic displacements, and the interactions are subsequently used in thermodynamic simulations. It is shown that the calculated atomic and magnetic short-range order accurately reproduces the results of neutron-scattering experiments. In particular, it is confirmed that the alloy exhibits a tendency toward ordering and the corresponding ordered phase is revealed. The magnetic structure is represented by spin-spiral clusters accompanied by weaker ferromagnetic short-range correlations. The spin-glass transition temperature obtained in Monte Carlo simulations by a finite-size scaling technique, 57 K, is in reasonable agreement with experimental data, 78 K.