Characterization and analysis of the training effect of exchange biasin coupled Ni Fe ∕ Ir Mn bilayers

The training effect of the so-called exchange bias in coupled polycrystalline Ni Fe ∕ Ir Mn thin films has been experimentally and theoretically investigated. A different formula is used to describe the exchange bias dependence on the measurement cycle number. It can be understood to be a consequence of the antiferromagnetic domain dynamics based on the Kolmogorov-Avrami [ Izv. Akad. Nauk, Ser. Math. 3 , 355 ( 1937 ) ; J. Chem. Phys. 8 , 212 ( 1940 ) ] model, which describes the nucleation and growth of antiferromagnetic domains in the film structures.