Exchange bias: The antiferromagnetic bulk matters

Abstract

Using controlled ion bombardment, the contribution of interface and bulk antiferromagnetic spins to exchange bias (EB) is investigated. Several sets of ferromagnetic (FM)/antiferromagnetic (AFM) (Ni/FeF2) bilayers capped with a nonmagnetic and inert Au layer of varying thickness were grown simultaneously. He-ion bombardment was employed to selectively create defects in the EB structure at the FM/AFM interface or in the AFM bulk. Numerical simulations provide the depth profile of the ion damage. Quantitative structural and magnetic characterizations were compared before and after the bombardment revealing the relationship between interfacial and bulk located defects. These studies show that the creation of defects in the bulk of the antiferromagnet crucially affects the magnitude of EB.