Thickness-Dependent Magnetization Reversal Behavior of Lithographic IrMn/Fe Ring Structures

We systematically studied the effect of exchange bias (EB) on the magnetization reversal behavior in lithographic IrMn/Fe rings and their unbiased Fe counterparts, with the thickness of the Fe layer, t Fe , varying from 10 to 80 nm. For unbiased and exchange biased rings, an evolution in the shape of the hysteresis loop from single-step to double-step is observed as t Fe increases. However, for EB rings, this transition happens at larger thickness, which is attributed to the uniaxial anisotropy induced by exchange bias in the Fe layer. The strength of the magnetic anisotropy induced by exchange bias is investigated by fitting the angular dependence of the exchange bias field H eb at different Fe thickness.