The effect of capping layer Ta on magnetic behaviour for multilayers Ta/Co/Co 3O 4/Ta

Abstract

Ta/Co/Co 3O 4/Ta and Ta/Co/Co 3O 4 multilayers were fabricated in a magnetron sputtering system under the same experimental conditions. The exchange bias field H E of Ta/Co/Co 3O 4/Ta was found obviously higher than that of Ta/Co/Co 3O 4. The results of XPS showed that some Ta atoms of capping layer in Ta/Co/Co 3O 4/Ta diffused into Co 3O 4 layer and reduced most of Co 3O 4 to CoO and a minor part to metallic Co, and introduced some non-magnetic defects of Ta oxide into the AFM layer. The effective thickness of interfacial layer CoO was evaluated according to the finite-size effect. Two possible reasons of enhancement of H E by Ta capping layer were proposed. The dilution of the AFM layer by Ta oxide may lead to the formation of AFM domains and some surplus magnetization to enhance H E. The metallic Co enchased in CoO matrix may lead to an increase of FM–AFM interface for the enhancement of H E.