Experimental Studies of Surface and Interface Magnetism by Spin Polarized Electron Techniques

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This research program is concerned with the spin dependent scattering of low-energy electrons from magnetic surfaces, and with the magnetic structure at interfaces of ferromagnetic and antiferromagnetic materials. The role of magnons in low-energy electron scattering in magnetic materials is largely unexplored. A high-resolution electron energy loss spectrometer (EELS ) will be built and combined with a spin polarized electron source to measure these spin dependent excitations. The exchange coupling at ferromagnetic/antiferromagnetic interfaces is of current interest in a range of contexts. For example, atomic scale roughness can lead to frustration and can drive magnetic reorientation transitions of the ferromagnetic film. This project will study the temperature dependent microscopic magnetic structures in ultrathin ferromagnetic films by magnetic microscopy and complementary structural characterization by STM and AFM. Graduate students will be trained in state of the art sample preparation and characterization techniques that prepare them for research positions in academic, government or industry laboratories.%%%A new field of electronic devices based on spin dependent transport in magnetic nanostructures is currently emerging under the name of "spintronics". In these devices the electrical properties depend on the magnetic structure of magnetic materials with layer thickness of nanometers. In these magnetic materials, electrons can lose energy by exciting spin waves (magnons) in the material. These processes, currently largely unexplored experimentally, are potentially very important in determining the materials' electrical properties. In this project, electrons will be scattered off magnetic surfaces and their energy losses studied. Use of a spin polarized electron beam allows one to distinguish between magnetic and non-magnetic excitations.At interfaces of different magnetic materials the magnetism can be dominated by the magnetic coupling between the materials. This can lead to unusual magnetic properties of ultrathin magnetic films. These effects depend sensitively on the interface quality, e.g. atomic scale roughness. This program will combine magnetic microscopy and STM to study the interplay between topography and micro-magnetic structure in magnetic thin films in contact with antiferromagnetic substrates. Students will be trained in cutting-edge materials preparation and advanced measurement techniques that prepare them for academic or industrial research in Materials and Applied Physics.