Spin polarized LEED rotation curves and spin dynamics of bulk Fe and Fe(100) films

Spin-polarized low-energy-electron-diffraction (SPLEED) has been proven to be a mature and unique tool to study magnetic surface. In this study, we explore the information that may be extracted from SPLEED rotation curves. Here the polar angle of incidence of an unpolarized beam is held fixed, and the scattering plane is rotated so the azimuthal angle is scanned. The total intensity of the scattered beam is monitored, along with components of spin polarization in the scattered beam parallel and perpendicular to the scattering plane. Venus and collaborators have reported such data for the clean W(100) surfaces, and this surface covered by (ferromagnetic) Fe overlayers. We explore this system, with attention to the sensitivity of features in the rotation curves to aspects of surface geometry and surface magnetism. We find, for example, the polarization data to be very sensitive to interplanar spacings near the surface.; We also present theoretical studies of the spin dynamics of bulk Fe and of ultrathin Fe(100) films, within an empirical tight binding description of the one electron energies. We use a Slater-Koster parameterization of the bulk paramagnetic energy bands, and apply these to the film. Ferromagnetic ground states are generated by introducing intra-atomic Coulomb repulsion within the d shell of each atom. The intra-atomic Coulomb matrix elements are expressed in terms of three Racah parameters, whose values are chosen to describe the ferromagnetism of the bulk, which include the total magnetic moment, the fraction of total moment with {dollar}tsb{lcub}2g{rcub}{dollar} and {dollar}esb{lcub}g{rcub}{dollar} characters. After this is done, we use the same parameters to calculate the ground state properties for a seven layer Fe(100) film.; All of the relevant information about the dynamics of the spin system are contained in the dynamic susceptibility {dollar}chi(vec q,omega).{dollar} And this quantity can be measured directly. We calculate the transverse dynamic spin susceptibility of both the bulk and a film with a (100) surface, within the random phase approximation (RPA). Such an approach describes the spin wave excitations of these systems, and their Stoner spectrum as well.