L10 FePt pinned spin valves (SVs) with different pinning/pinned layers: FePt/CoFe, FePt/Ru/CoFe, and FePt/CoFe/Ru/CoFe, were fabricated and investigated. Samples with rigidly ferromagnetic coupled bilayer of FePt (6.0 nm)/CoFe (4.0 nm) show giant magnetore-sistance (GMR) ratio up to 7.06%, which is similar to that in the conventional Mnlr-based SVs. Whereas the free layer coercivity (Hcf) of CoFe (3.0 nm)/NiFe (4.0 nm) is as high as 45 Oe. This is mainly due to the exchange coupling between the free layer and (111) textured FePt layer. Synthetic antiferromagntic structures, FePt/Ru/CoFe and FePt/CoFe/Ru/CoFe, were proved to be very effective in reducing the H cf value by forming a closed flux pathway in the bottom electrode. Compared with FePt/Ru/CoFe SVs, the FePt/CoFe/Ru/CoFe ones show higher pinned layer switching field. The optimized SV structure in this study is glass/FePt (6.0)/CoFe (2.0)/Ru (0.8)/CoFe (2.5)/Cu (2.4)/CoFe (3.0)/NiFe (4.0)/Pt (2.0) (in unit of nm), which exhibits a GMR ratio of 7.04%, a free layer Hcf of 22 Oe, and a pinned layer switching field of 1824 Oe.
Bibliographical noteFunding Information:
This work was supported by the National Nature Science Foundation of China under Grants 10604016, 10374019, 60678008, and 60490290, and the Science and Technology Committee of Shanghai under Grants 05PJ14016 and 06DJ14007.
- Giant magnetoresistance
- L1 FePt
- Spin valve
- Synthetic antiferromagntic coupling