Thermal stability of Ir-Mn as exchange biasing material

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 conf igurations with the Ir-Mn layer both below and above the ferromagnetic (F) layer. The highest interfacial exchange energy (J(eb) = 0.13 mJ/m(2) at 300 K) was found for 10 nm Ir-Mn deposited above a Co90Fe10 layer. For all con figurations 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 remarka ble decrease of the exchange biasing at room temperature was found after he ating the film, whereas such an effect was not observed for a 10 nm thick I r-Mn layer deposited below the F layer. This observation, in combination wi th the results of a relaxation experiment and the lack of experimental evid ence for structural changes upon heating, suggests that heating can induce an irreversible change in the magnetic structure of Ir-Mn layers. (C) 1999 American Institute of Physics. [S0021-8979(99)31608-X].