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(S nm)/NiFe(2 nm)/CoZrNb(10 nm)/(or = 2, 2.3, 2.6 nm). prepared by the sputtering method, showed the crystal structure of a fcc (111) preferred orientation. As-deposited CoFe spin valves with Ir-Mn exhibited an interfacial exchange coupling energy of J = 0.192 erg/cm² (H_ua ∼ 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 °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 °C increased to 400 Oe. The decrease in H_ua was not observed after second annealing and seems to be stabilized by first annealing.