Study of energetic and magnetic properties of Fe$_{x}$Ni$_{1-x}$ monolayer film on nonmagnetic metallic substrates

Within the variational spin density functional method, the description of the temperature and ferromagnetic ordering effects on the adsorption of atoms of transition metals placed on paramagnetic substrates at formation of a monolayer film of Fe$_{x}$Ni$_{1-x}$ alloy depending on the alloy component concentration and the coating parameter $\theta$ has been accomplished for the first time. The influence of different orientations of substrate surface planes is studied. The adsorption energy of a close-packed plane is minimal for all the systems presented. It is shown that a monolayer film without mixing is formed on the Au and W substrates at large values of the coating parameter and iron concentration, while silver atoms are forced out to the surface of the Ag substrate. The comparison of values of the adsorption energy calculated at $\theta=1$ and $T$ = 0 K is carried out within the variational and the first-principles approaches. The calculation of magnetic moments and parameters of exchange interaction of the Fe$_{x}$Ni$_{1-x}$ bulk alloy using the Korringa–Kohn–Rostoker method is accomplished at the equilibrium values of lattice constant obtained within the first-principles calculations. The exchange interaction is of a ferromagnetic nature, it increases with the increase in nickel concentration in the nearest polytypic neighbors $J_{1}^{\mathrm{Ni-Fe}}$ and decreases in the nearest equitype neighbors $J_{1}^{\mathrm{Ni-Fe}}$. The exchange interaction between the second neighbors occurs only in equitype atoms; it is of a ferromagnetic nature in iron atoms and is weakly antiferromagnetic in nickel atoms.