Direct evidence of imprinted vortex states in the antiferromagnet of exchange biased microdisks

The magnetic domain structure of patterned antiferromagnetic/ferromagnetic Ir(20)Mn(80)/Ni(80)Fe(20) bilayer microdisk arrays has been investigated using layer-specific polarized x-ray photoemission electron microscopy and magnetic circular dichroism. Magnetic imaging at the Fe and Mn L-edge resonances provided direct evidence of a vortex state imprinted into the antiferromagnet at the interface. The opposite magnetic contrast between the layers indicated a reversed chirality of the imprinted vortex state, and a quantitative analysis of the magnetic moment from the dichroism spectra showed that uncompensated Mn spins equivalent to about 60% of a monolayer of bulk Ir(20)Mn(80) contributed to the imprinted information at the interface. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3168515]