L 10 -ordered FePt alloy is introduced into the synthetic antiferromagnetically coupled spin valves as an exchange pinning layer. Large switching field of 1824 Oe for the reference layer and a high giant magnetoresistance (GMR) ratio of 7.0% are observed in such FePt-pinned spin valves, which are comparable to those in MnIr-pinned samples with similar structures. However, the GMR ratio in FePt-pinned spin valve exhibits a poor thermal stability. The rough surface of the FePt layer causes the atoms to interdiffuse easily at lower temperature, resulting in some FePt formation in the CoFe reference layer. This magnetic isotropic FePt alloy with (111) texture could degrade the uniaxial anisotropy of the reference layer, leading to the reduction of GMR ratio.
Bibliographical noteFunding Information:
This work was supported by the National Nature Science Foundation of China (Grant Nos. 10604016, 10374019, 60490290, and 60678008) and grants from the Science and Technology Committee of Shanghai (Nos. 05PJ14016 and 06DJ14007). The authors thank Professor Shiming Zhou in Physics Department of Fudan University for the VSM measurements.