Correlating uncompensated antiferromagnetic moments and exchange coupling interactions in interface ion-beam bombarded Co90Fe 10/CoFe-oxide bilayers

The coercivity and exchange bias field of ferro-/antiferromagnetic Co 90Fe10/CoFe-oxide bilayers were studied as function of the surface morphology of the bottom CoFe-oxide layer. The CoFe-oxide surface structure was varied systematically by low energy (0-70 V) Argon ion-beam bombardment before subsequent deposition of the Co90Fe10 layer. Transmission electron microscopy results showed that the bilayer consisted of hcp Co90Fe10 and rock-salt CoFe-oxide. At low temperatures, enhanced coercivities and exchange bias fields with increasing ion-beam bombardment energy were observed, which are attributed to defects and uncompensated moments created near the CoFe-oxide surface in increasing amounts with larger ion-beam bombardment energies. Magnetometry results also showed an increasing divergence of the low field temperature dependent magnetization [ΔM(T)] between field-cooling and zero-field-cooling processes, and an increasing blocking temperature with increasing ion-beam bombardment energy. © 2012 The Japan Society of Applied Physics.