Micromagnetic calculation of bias field and coercivity of polycrystalline ferromagnetic/antiferromagnetic layers

Domain processes associated with exchange bias in ferromagnetic /antiferromagnetic layers are investigated using a micromagnetic approach. The model gives quantitative estimates of the bias field and the coercivity for bilayers with fully compensated interfaces. Both simulations and transmission electron microscopy studies of IrMn-NiFe systems show 360° wall loops and 360° wall segments during the reversal of the F layer. The calculated bias field is in range of μ₀H_eb=3 mT to μ₀H_eb=20 mT. The bias field shows a maximum as a function of the antiferromagnet (AF) thickness. It increases sharply with increasing AF thickness at low thicknesses and decreases moderately with increasing AF thickness at higher thicknesses.