Competing magnetic interactions in exchange bias modulated films

Abstract

The magnetization reversal in stripe-like exchange bias patterned $\rm Ni_{81}Fe_{19}/IrMn$ thin films was investigated by complementary inductive and high resolution magneto optical magnetometry, magneto optical Kerr microscopy, and polarized neutron reflectometry to clarify the effects of competing interfacial exchange bias and lateral interface contributions. Structures of varying ferromagnetic layer thickness and stripe period were analyzed systematically at the frozen-in domain state of oppositely aligned stripe magnetization. For all samples the mean magnetization of the magnetic hybrid structures was found to be aligned nearly orthogonally with respect to the stripe axis and the set exchange bias direction. Due to the interaction of interfacial coupling, exchange, and magneto-static energy contributions, the opening angle of neighboring stripe magnetizations increases with decreasing ferromagnetic layer thickness and increasing stripe period. The experimental observations are in agreement with an earlier proposed model for designing micro-patterned exchange bias films.