Spin-flop coupling and rearrangement of bulk antiferromagnetic spins in epitaxial exchange-biased Fe/MnPd/Fe/IrMn multilayers

The role of bulk antiferromagnetic spins on exchange bias was investigated in interface spin-flop coupled Fe/MnPd bilayers and Fe/MnPd/Fe/IrMn multilayers. Magnetic measurement of the bilayers showed that the exchange bias saturated at a uniquely large critical thickness, similar to 300 angstrom, with a spin reorientation transition simultaneously observed. Field cooling of the multilayer, with parallel or antiparallel alignment of the two Fe layers leads to a different MnPd internal spin arrangement. Minor loop studies showed that nonrecoverable changes in the spin structure of the antiferromagnet occurred during the Fe layer reversal. The possibility of manipulating exchange bias of the Fe/MnPd couple by modifying the MnPd bulk spin configuration using the magnetizing process of the Fe/IrMn couple is demonstrated. A qualitative model based on interface spin-flop coupling is proposed to explain all the relevant properties, including the temperature dependence of the exchange bias.