Effects of the shape anisotropy on the giant magnetoresistance properties

For the application of giant magnetoresistance (GMR) devices such as magnetic recording head or magnetic field sensors, spin valves are patterned on micron scales. In an attempt to understand shape anisotropy effect and switching behaviors of patterned structure, we measured GMR responses of patterned stripes with different aspect ratios and angular dependence of GMR responses with respect to the applied field angles. In case of lower aspect ratio (20:6), MR ratio decreased gradually with the increase in angle between applied field and pinning direction. In case of high aspect ratio (20:2), MR ratio did not decrease up to a certain angle, after that down to the lower value rapidly. In addition, there is increase in coercivities of free and pinned layers, which is due to the shape anisotropy with respect to the high aspect ratio. This trend agrees well with the simulated GMR curves using single domain model where we consider on self-demagnetization and interlayer magnetostatic coupling effects.