Polarized neutron studies on exchange-bias micro-stripe pattern

Abstract

In the present study we examined the results of competing interactions in laterally exchange biased modulated thin films. For studying the magnetic interactions between neighboring magnetic elements we designed a model system. Considering that the model system should be of technological interest on the one hand, and should allow the application of several different and efficient experimental techniques for complementary analysis on the other hand, we have chosen films with in-plane stripe-like magnetic domains. The evolution of the magnetic domain structure along the hysteresis loop was analyzed with a combination of experimental techniques: magneto-optical Kerr effect, Kerr microscopy, polarized neutron reflectometry, and off-specular scattering of polarized neutrons with polarization analysis.Due to the competition between interfacial exchange bias at the ferromagnetic-antiferromagnetic interface and intra-layer exchange interactions between neighboring ferromagnetic stripes the alignment is not perfectly antiparallel, but is periodically canted with respect to the stripe axis. Thus the net magnetization of the ferromagnetic film turns almost perpendicular to the stripes. At the same time the projection of the magnetization vector onto the stripe axis has a periodically alternating sign. The experimental observations are explained and quantitatively described within the frame of a phenomenological model. The model defines conditions which can be used for tailoring nano- and micro-patterned EB systems with different types of magnetic order.