Magnetization processes in spin-valve meanders for sensor applications

We used Kerr microscopy to investigate the magnetization processes of NiFeCo/Cu/Co/FeMn spin-valve meanders for magnetoresistive sensors and compared them to processes in related single films and bilayers. We observed irregular switching, characterized by the irreversible decay of blocked domains or by domain nucleation at 360° walls, in the related films and in the free layer of the spin-valve system. Both effects are connected with hysteresis. Edge-curling walls are responsible for rotational hysteresis in the giant magnetoresistance signal of the spin valves, occurring during field rotation in clockwise and counterclockwise directions. The U-turns of the meanders and their shape have no relevant influence on the magnetization behavior and hysteresis effects.