Spin Transfer in Magnetic Nanopillars

This thesis describes experimental studies of spin-transfer induced magnetization switching and dynamics in bilayer magnetic nanopillars. Known as the spin transfer effect, a spin-polarized current can transfer its angular momentum to a magnetic layer, resulting in its reversal as well as microwave dynamics. It has become a major focus in both physics and technology. Our nanostructured spin valve junctions are fabricated using two different processes. The first one is the nanostencil process, where pillar structures are deposited into pre-defined stencil holes with submicron lateral dimensions, and extended leads are patterned using lithography. The other one is the subtractive process, where pillar structures are formed by etching pre-deposited magnetic films. Junctions were patterned so that current flows perpendicularly to the layer surface. Low frequency transport measurements were conducted on asymmetric Co/ Cu/ Co spin valve junctions with large perpendicular applied magnetic field to study the current needed to excite magnetization dynamics as a function of thin magnetic layer thickness. The critical current density decreases as the free layer