Role of anti-ferromagnetic layer thickness in exchange bias: case study of Co/CoO with Kerr microscopy

Abstract

Exchange bias (HEB) and the magnetic training effect behavior of Co/CoO bilayer system with the different anti-ferromagnetic (AFM) layer thickness (tCoO = 5, 8.8 and 12.3 nm) is investigated by Kerr microscopy and it is found that the magnitude of HEB is more or less constant, but the training effect varies considerably with the AFM layer thickness. Moreover with increasing AFM layer thickness, HEB decreases more gradually with the consecutive cycling indicating that the AFM interface relax more slowly with the cycling suggesting that the increasing AFM layer thickness offer more stability to the interface coupling in conventional exchange bias systems. Kerr microscopy results reveals that there seems to be a deviation of AFM interface magnetization or pinning direction from its initial field cooling configuration for the lower AFM layer thickness, whereas for higher AFM thickness only change in domain state of AFM layer is evident with consecutive cycling.