Structural and magnetic studies of exchange bias films of Ir(20)Mn(80)

Thin films of IrMn were made by magnetron sputtering, using nominally 20 at . % Ir, and their structural and magnetic properties were evaluated for use as an exchange bias material. The magnetic properties of different combina tions of Py and CoFe underlayers were determined by magnetometry and by usi ng ferromagnetic resonance (FMR) in the temperature range 4-350 K; x-ray an alyses and atomic force microscopy were used to assess the structures. The IrMn films have the AuCu3 structure with strong < 111 > texture. The intern al interfaces of the multilayer structures are very smooth. They induce rel atively strong exchange bias in Py and CoFe overlayers but can have negligi ble coercivity. The bias field is strongly dependent on the direction of th e moment during cooling, even well below 300 K, and coercivity and FMR line width increase with cooling. Isotropic shifts of FMR are small at 300 K but increase rapidly below 150 K. Our data suggest that spin-flop models for e xchange bias may not apply to IrMn, and that small spin structures dominate low temperature behavior. [S0021-8979(00)35808-X].