Spin Dynamics of Itinerant Electron Ferromagnetic Nanostructures

We review our theoretical studies of the spin dynamics of ultrathin ferromagnetic films adsorbed on metallic substrates. Of interest are the spin waves with wave vector from the center of the Brillouin zone to its boundary. We utilize a realistic electronic structure for the substrate/adsorbate combination through an empirical tight binding description of the electronic structure of the materials involved, and the spin excitations are explored through the random phase approximation. We can examine very large systems with this scheme, such as multilayer films placed on fully semi-infinite substrates. One principal finding is the adiabatic approximation breaks down qualitatively for these systems. We illustrate for Co films on Cu(100) where we also find excellent agreement with experiment. We conclude by discussing recent data for the Fe bilayer on W(110) where, after an excellent account of the measured exchange stiffness, we find the large wave vector spin waves generated by theory to be far too stiff.