Interface induced manipulation of perpendicular exchange bias in Pt/Co/(Pt,Cr)/CoO thin films

Perpendicular exchange bias has been manipulated by changing ferromagnetic film thickness and spacer layer in Pt/Co/(Pt,Cr)/CoO thin films. The exchange bias characteristics, blocking temperature, and magnetization of thin films strongly depend on the spacer layer (Pt,Cr) between ferromagnetic and antiferromagnetic layers. While Pt/Co/Pt/CoO thin films show perpendicular exchange bias, Pt/Co/Cr/CoO has exchange bias with easy magnetization axis in the film plane. We have also observed very small hysteretic behavior from the hard axis magnetization curve of Pt/Co/Cr/CoO film. This can be attributed to misalignment of the sample or small perpendicular contribution from Pt/Co bottom interface. We have also investigated the temperature and spacer layer dependent exchange bias properties of the samples. We observed higher H_EB and H_C for the thicker Co layer in the Pt/Co/Pt/CoO sample. In addition, onset of exchange bias effect starts at much lower temperatures for Pt/Co/Cr/CoO thin film. This clearly shows that Cr spacer layer not only removes the perpendicular exchange bias, but also reduces the exchange interaction between Co and CoO and thus lowers the T_B. - Highlights: • PEB has been manipulated by changing FM film thickness and spacer layer. • EB characteristics, T_B, strongly depend on the spacer layer. • Higher H_EB and H_C for the thicker Co layer was observed in the Pt/Co/Pt/CoO sample. • Cr spacer layer not only removes PEB but also reduces the exchange interaction