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

http://apl.aip.org/resource/1/applab/v95/i1/p012510_s1
Appl. Phys. Lett. 95, 012510 (2009)
G. Salazar-Alvarez, J. J. Kavich, J. Sort, A. Mugarza, S. Stepanow, A. Potenza, H. Marchetto, S. S. Dhesi, V. Baltz, B. Dieny, A. Weber, L. J. Heyderman, J. Nogués, and P. Gambardella doi:10.1063/1.3168515

Abstract:
The magnetic domain structure of patterned antiferromagnetic/ferromagnetic Ir₂₀Mn₈₀/Ni₈₀Fe₂₀ 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 Ir₂₀Mn₈₀ contributed to the imprinted information at the interface.