Spin dynamics and magnonic characteristics of a magnetically ordered fcc Fe-Ni alloy monolayer on an fcc Ni slab substrate

•Spin dynamics of magnetically ordered monolayer of Fe-Ni alloy on fcc Ni substrate.•Nearest and next nearest spin exchange parameters obtained via the SPRKKR code.•The local density of states obtained via the PFMT and Green’s formalism.•Five dispersion branches for magnons propagating along the y-direction.•Fe-Fe interactions cause a small increase in the highest mode of the dispersion curve. We investigate the surface spin dynamics and magnonic characteristics of a magnetically ordered fcc Fe-Ni alloy monolayer on a Ni magnetic slab substrate. The calculations are performed using the Heisenberg Hamiltonian representation for the magnetic ground state of the system. Using the Spin Polarized Relativistic Korringa-Kohn-Rostoker (SPRKKR) method, the relevant magnetic exchange parameters are computed, taking into account the nearest and next nearest Fe-Fe interactions. This establishes the appropriate Heisenberg Hamiltonian. The Phase Field Matching Theory (PFMT) is applied to compute the spin dynamics and surface magnonics of the system, and thus determine the spin wave eigenmodes localized at the surface but propagating in its plane with surface group velocities; these intrinsic eigenmodes constitute basic elements for the magnonic characteristics of the system. The inclusion of the Fe-Fe interactions alters the highest magnonic mode compared to the case when such interactions are absent. The localized densities of states (LDOS) for the irreducible representative magnetic sites at the surface nanostructure are extracted from our computed PFMT Green’s functions. The model is general, and can be applied to different ultrathin layered magnetic alloys on magnetically ordered substrates.