Magnetic interactions in systems with reduced dimensionality

• Main Author: Brewer, Matthew S.
• Published: University of Warwick 2014
• Subjects: 530; QC Physics
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606198

Detailed knowledge of the interaction of magnetic moments is key to developing the next generation of magnetic devices. Systems with induced moments provide an ideal regime in which to study this fundamental behaviour. Resonant x-ray scattering and polarised neutron reflectivity are complementarily used to map induced moment profiles in continuous FeZr/CoZr multilayer films and both continuous and patterned Pd/Fe/Pd trilayer films. Resonant scattering is additionally employed to measure the dimensionality of the magnetic lattice through observations of the magnetic ordering behaviour. The shape and extent of the induced profiles was resolved with unprecedented accuracy, and was found to conform to the theoretical expectation: all profiles decayed exponentially from the inducing material, with an extent in the nm regime. Adjacent magnetic lattices were found to interact only through the magnitude of their moments, acting through the magnetic susceptibility of the induced material. The dimensionality of adjacent magnetic lattices were therefore found to be independent. Additionally, a significant, and unexpected, observation was made of the thinnest Fe layers studied: the Fe moment was seen to vanish though a pronounced induced moment remained in the neighbouring Pd. The definitive cause of this unusual behaviour has yet to be discovered. In the patterned materials, the interaction between adjacent islands was found to contribute minimally to the overall behaviour in the geometry studied. The energy cost of rotating the moments within an individual island was the dominating contribution to the magnetic ordering behavior. These results provide new insight into the coupling mechanisms between adjacent moments, while revealing new complexities that provide the foundation for further study.