Ferromagnetic relaxation in spin valves with picoscale antiferromagnetic layers

We have investigated the mechanism of weak exchange bias for a spin valve with threshold layer antiferrornagnetic (AFM) thickness using giant magnetoresistance (GMR) and polarized neutron reflectometry (PNR). Results show that the sample exhibits instantaneous switching of the free layer followed by a gradual reorientation of the magnetization in the pinned ferromagnetic layer via domain wall formation. During subsequent field cycles, we found that relaxation in the pinned ferromagnetic (FM) layer is induced not only by an increasing field, but also in a static field over a relatively long time scale.