Thermal stability of α-Fe2O3/CoFe/Ru/CoFe-based spin valves

Magnetoresistive (MR) properties of alpha-Fe2O3-based spin valves with and without a CoFe/Ru/CoFe synthetic antiferromagnet (SAF) were studied at elevated temperatures and after the annealing in different conditions. The pinning field of the spin valve consisting of alpha-Fe2O3(20 nm)/CoFe(2 nm)/Ru(0.7 nm)/CoFe(2 nm)/Cu(2 nm)/ CoFe(1 nm)/NiFe(5 nm)/Ta(3 nm)was larger than 300 Oe at 200 degrees C, which was about five times as much as that of the spin valve consisting of alpha-Fe2O3(20 nm)/CoFe(2 nm)/Cu(2 nm)/CoFe(1 nm)/NiFe(5 nm)/ Ta(3 nm). The MR ratio and sheet resistance change in the alpha-Fe2O3(20 nm)/CoFe(2 nm)/Ru(0.7 nm)/CoFe(2 nm)/Cu(2 nm)/ CoFe(0.5 nm)/NiFe(3 nm)/Ta(3 nm)film were 9.8% and 2.6 Omega/square, respectively, after annealing at 270 degrees C for 3 h. The simple spin-valve structure with the same composition also showed good thermal stability of MR properties against annealing at 200 degrees C without an applied magnetic field. (C) 2000 American Institute of Physics. [S0021-8979(00)56108-8].