Magnetization dynamics in ultrathin magnetic films

Ultrathin magnetic multilayer structures are prepared by Molecular Beam Epitaxy (MBE) on GaAs(001) substrate. Growth is monitored and characterized by Reflection High Energy Electron Diffraction (RHEED), Auger Electron Spectroscopy (AES), X-Ray Photoelectron Spectroscopy (XPS) and Scanning Tunneling Microscopy (STM). The interface of Fe/GaAs system and its influence on the static magnetic properties in magnetic ultrathin films were studied by means of FMR and Mossbauer spectroscopy. Studies were performed on high quality single crystalline magnetic films. It will be shown that in ultrathin magnetic films magnetic properties are governed by a combination of interface and bulk effects. Static and dynamic magnetic properties of magnetic single and double layers were studied using Ferromagnetic Resonance (FMR) and Time Resolved Magneto-optic Kerr Effect (TRMOKE) in a wide range of microwave frequencies. Magnetic damping was studied in Au/Fe/GaAs structures as a function of the thickness of magnetic Fe layer and as a function of the capping Au layer. Spin currents generated by spin pump/spin sink effect structures were extensively investigated in magnetic doublelayer. Pure spin current driven dynamics in magnetic doublelayers was observed using TRMOKE technique. The spin diffusion and spin accumulation analysis was applied to explain spin momentum propagation in the normal metal. Spin diffusion length in Au was measured via direct observation of magnetic moment transfer. Spin pump/spin sink theory was tested for antiparallel driving of two magnetic layers of the magnetic doublelayer structure. This extreme condition was achieved via patterning sample into a coplanar waveguide. Results are in good agreement with simulations based on theory, which includes spin pump/spin sink model together with diffusive transport of accumulated spin momentum through the non-magnetic layer. Au/Fe/Au/Fe/GaAs magnetic double layer structure was used to study spin pump/spin sink effect in case of non-collinear orientation of magnetic moments. It will be shown that only component of spin momentum which is transverse to static magnetization contributes to non-local dynamics.