Coercive mechanism and training effect in Fe-Au/Ni-Fe bilayer films

Abstract

Exchange bias effect in spin glass/ferromagnetic systems has been studied recently. Here, we report the coercive mechanism and training effect in Fe-Au/Ni-Fe films. Experimental results indicate that the coercivity (H c) mainly originates from direct coupling between Fe-Au and Ni-Fe layers at temperatures (T) well below the blocking point (T b). At T near T b, H c comes from spin-flop coupling and defects in the Ni-Fe layer. The findings confirm the validity of our spin structure model. Additionally, irreversible rearrangement of Fe-Au spins from the field cooling state was indicated by the training effect of both Fe-Au/Ni-Fe and Fe-Au powder samples. The results are discussed in detail.