UC Berkeley

This dissertation explores interface interactions, topology of spin structures, and the use of interface interactions in manipulating the topology of spin structures. First, I will present our work on interface interactions in magnetic thin film heterostructures. A majority of interesting phenomena in magnetic heterostructures are caused primarily by the interface interactions. In exchange bias system CoO/MgO/Fe/Ag(001), the role of frozen and rotatable antiferromagnetic spins in exchange bias system was investigated using X-ray Magnetic Linear Dichroism (XMLD). In the Py/FeMn/Ni/Cu(001) system, the indirect coupling through an antiferromagnetic spacer layer was studied through anisotropy measurements using Rotating-Field Magneto-Optical Kerr Effect (ROTMOKE).

Second, I will present our work on artificial topological spin structures. Traditionally, research on nanostructured magnetic materials has focused on the study of uniformly magnetized thin films. With the increasing capability to prepare and manipulate non-uniform spin configurations in recent years, various topological spin structure have been realized. In magnetic thin films, magnetic vortex states can be stabilized by reducing the lateral dimension of the magnetic thin film to the nanoscale due to the increased shape anisotropy. By combining this shape anisotropy and interlayer exchange coupling at the interface, we showed that more complex topological spin structures such as spin skyrmions and hedgehog spin merons can be stabilized and manipulated. By utilizing uniaxial strain in a ferroelectric-ferromagnetic system Co/Cu/PMN-PT(011), we demonstrated a method to manipulate the circulation of a magnetic vortex state using strain.