Polarized neutron reflectometry study on a magnetic film with an ion beam imprinted stripe pattern

Theis-Broehl K, Toperverg BP, Westphalen A, et al. Polarized neutron reflectometry study on a magnetic film with an ion beam imprinted stripe pattern. In: Superlattices and Microstructures. SUPERLATTICES AND MICROSTRUCTURES. Vol 41. ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD; 2007: 104-108.We used polarized neutron reflectometry for a quantitative study of the field dependent arrangement of the magnetization vector in the different regions of an ion beam imprinted stripe pattern in a magnetic film. For the magnetic patterning of the Co70Fe30 film we took advantage of the exchange bias to an antiferromagnetic Mn83Ir17 layer which was changed locally by He-ion bombardment. The exchange bias was set to be antiparallel in the two different striped regions. We found that after magnetization reversal of half of the stripes the magnetization in neighbouring regions is periodically canted with respect to the stripe axis so that the net magnetization of the ferromagnetic film tums almost perpendicular to the stripes. At the same time the projection of the magnetization vector onto the stripe axis has a periodically alternating sign. (c) 2007 Published by Elsevier Lt

Self-assembled iron oxide nanoparticle multilayer: x-ray and polarized neutron reflectivity

We have investigated the structure and magnetism of self-assembled, 20 nm diameter iron oxide nanoparticles covered by an oleic acid shell for scrutinizing their structural and magnetic correlations. The nanoparticles were spin-coated on an Si substrate as a single monolayer and as a stack of 5 ML forming a multilayer. X-ray scattering (reflectivity and grazing incidence small-angle scattering) confirms high in-plane hexagonal correlation and a good layering property of the nanoparticles. Using polarized neutron reflectivity we have also determined the long range magnetic correlations parallel and perpendicular to the layers in addition to the structural ones. In a field of 5 kOe we determine a magnetization value of about 80% of the saturation value. At remanence the global magnetization is close to zero. However, polarized neutron reflectivity reveals the existence of regions in which magnetic moments of nanoparticles are well aligned, while losing order over longer distances. These findings confirm that in the nanoparticle assembly the magnetic dipole-dipole interaction is rather strong, dominating the collective magnetic properties at room temperature. Accession Number: WOS:00029931600002