The coercivity and exchange bias field of ferro-/antiferromagnetic Co₉₀Fe₁₀/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.