Energy of mixing and magnetic state of components of Fe-Mn alloys: A first-principles calculation for the ground state

Methods of first-principles computer simulation have been used to calculate the magnetic moments at the component atoms and the energies of mixing in substitutional fcc and bcc solid solutions of manganese in iron. It has been established that the energies of mixing in α and γ solid solutions have not only different magnitudes but even different signs. It is shown that in α solid solutions there is a thermodynamic anomaly at a manganese concentration of approximately 1.5 at. %, namely, a change in the concentration dependence of the energy of mixing caused by a reorientation of magnetic moments at manganese atoms. With increasing Mn content in dilute solutions, there occurs a continuous variation of the orientation of magnetic moments of manganese atoms from strictly antiparallel with respect to the ferromagnetic iron matrix to predominantly parallel one.