Probing Exchange Bias Properties of Pt x Co1−x /Pt/CoO Films

Abstract

We present magnetic properties of bilayers consisting of antiferromagnetic CoO and ferromagnetic Pt x Co1−x film structure on Si (001) as Pt/PtCo/Pt/CoO/Pt. The CoO layer and the Pt x Co1−x layer thickness were kept constant (10 nm). In order to prevent PtCo ferromagnetic layer from oxidation, thin Pt (4 A) spacer layer was grown between PtCo and CoO layers. The chemical composition of Pt x Co1−x layers were changed from 0.1 to 0.5 and the exchange bias effect and blocking temperature of the structures were determined. Composition dependence of magnetization measurements showed that exchange bias effect took maximum value in Pt0.5Co0.5/Pt/CoO; on the other hand, its minimum value was observed on Pt0.3Co0.7/Pt/CoO. The spacer layer supplied positive contribution for exchange bias (EB) effect compared to bilayers without Pt spacer layer. The other result from composition-dependent measurements indicates that blocking temperatures exhibited oscillatory behavior and the highest value was obtained from Pt0.1Co0.9/Pt/CoO whereas the lowest value was measured from Pt0.3Co0.7/Pt/CoO. Blocking temperatures of all samples were lower than the Neel temperature of bulk CoO. According to these results, the manipulation of interface between PtCo and CoO layers gives us the possibility of tuning exchange bias effect with Pt concentration, temperature, and spacer Pt layer.