Spin-valve giant magnetoresistive films with antiferromagnetic Ir-Mn layers

We succeeded in developing CoFe spin valves with an antiferromagnetic Ir-Mn film. Ir-Mn single-layer films and spin valves of Ta(5 nm)/Ir-Mn(8 or 9 nm)/Co90Fe10(x nm)/Cu(3 nm)/Co90Fe10(3 nm)/NiFe(2 nm)/CoZrNb(10 nm)/(x = 2, 2.3, 2.6 nm), prepared by the sputtering method, showed the crystal structure of a fee (111) preferred orientation. As-deposited CoFe spin valves with Ir-Mn exhibited an interfacial exchange coupling energy of J = 0.192 erg/cm(2) (H-ua similar to 640 Oe at t(CoFe) = 2 nm), that was the highest ever reported for as-deposited antiferromagnetic films, such as NiO, NiMn, and FeMn. Furthermore, CoFe spin valves with Ir-Mn exhibited a higher blocking temperature of 260 degrees C, and a higher MR ratio of 6.37% than the spin valves with FeMn film. After annealing, the MR ratio increased to 7.82%. On the other hand, the H-ua decreased about 100 Oe after annealing. The H-ua-T curve was, however, improved and the H-ua at 100 degrees C increased to 400 Oe. The decrease in H-ua was not observed after second annealing and seems to be stabilized by first annealing. (C) 1997 American Institute of Physics.