Thermal stability of Ir–Mn as exchange biasing material

Abstract

We have investigated the strength and the thermal stability of Ir–Mn (18 at. % Ir) as an exchange biasing material for Ni80Fe20 and Co90Fe10, for configurations with the Ir–Mn layer both below and above the ferromagnetic (F) layer. The highest interfacial exchange energy (Jeb=0.13 mJ/m2 at 300 K) was found for 10 nm Ir–Mn deposited above a Co90Fe10 layer. For all configurations investigated the blocking temperature was approximately 560 K. For 10 or 30 nm Ir–Mn above and for 30 nm Ir–Mn below the F layer a remarkable decrease of the exchange biasing at room temperature was found after heating the film, whereas such an effect was not observed for a 10 nm thick Ir–Mn layer deposited below the F layer. This observation, in combination with the results of a relaxation experiment and the lack of experimental evidence for structural changes upon heating, suggests that heating can induce an irreversible change in the magnetic structure of Ir–Mn layers.