Quantum confinement and symmetry breaking in layered magnetic nanostructures

The effects quantum confinement and symmetry breaking are believed to play a crucial role in determining the magnetic properties of magnetic thin films and multilayers. We investigated the quantum confinement using Angle-Resolved Photoemission Spectroscopy (ARPES) and the symmetry breaking using the Surface Magneto-Optic Kerr Effect (SMOKE).;The quantum well (QW) states in a Cu thin film grown on a Co(001) substrate were directly observed using ARPES, which measured the momentum-resolved density-of-states. Using a wedged Cu film to vary the thickness of the QW, we observed a shifting of the QW energy levels that occurs in order to satisfy the standing wave boundary conditions along the normal direction. This behavior was analyzed within the framework of the phase accumulation model. In addition, we developed a method to map out the nodes and antinodes of the standing wave by inserting a monolayer of Ni into different positions inside the well. In terms of magnetic properties, the relation between the QW states and the oscillatory magnetic coupling was investigated by measuring both phenomena on the same sample. We also observed a quantum interference effect on the QW states which shows that the oscillations in the magnetic coupling strength with ferromagnetic thickness originate from a modulation of the QW density of states. We also examined the effects of in-plane motion, which leads to the QW subbands. Finally, a study of the electronic coupling in double QW systems shows that the length scale of tunneling across the hybridization gap is only a few atomic layers.;The step-induced magnetic anisotropy in Fe on stepped Ag(001) and Co on stepped Cu(001) was investigated using SMOKE. Regular atomic steps on a (001) surface break the four-fold rotation symmetry to induce an in-plane uniaxial magnetic anisotropy. To explore the intrinsic relation between the lattice symmetry breaking and the induced magnetic anisotropy, we developed a curved substrate that allowed a continuous range of vicinal angles to be present on a single sample. Previous studies only looked at a fixed vicinal angle. We found that the step-induced magnetic anisotropy strength varied quadratically with the step density for Fe/stepped Ag(001), but linearly for Co/stepped Cu(001). The results are analyzed within a nearest neighbor Neel pair-bonding model, which suggests that the differences are due to the differences in the local bonding of these two structures. Both pair-bonding and strain effects are analyzed.