Atomic resolution determination of spin configuration at interfaces in functional materials in the transmission electron microscope

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New energy-efficient information and communications technologies place ever-increasing demands on the performance of magnetic materials. The development of materials to meet these challenges requires an atomic-level knowledge of their local spin configurations, in order to predict and control their physical properties. In this Joint Sino-German Research Project, we will develop atomic-scale magnetic imaging and spectroscopy of the spin configurations at interfaces in functional materials, in order to obtain a fundamental understanding about the physical origins of novel magnetic coupling phenomena. Our approach involves the use of a combination of off-axis electron holography (EH), electron magnetic circular dichroism (EMCD), spatially-resolved electron energy-loss spectroscopy and chromatic aberration correction. Chromatic aberration correction, in particular, has the potential to improve spatial resolution in magnetic characterisation using both EH and EMCD to the atomic level. The combined use of these techniques promises to provide atomic-scale information about both in-plane and out-of-plane magnetization in the same material, thereby offering three-dimensional spin information at the high spatial resolution. The cooperative interplay between spin, charge, orbital and lattice degrees of freedom at interfaces will results in an atomic level experimental understanding of exchange spring magnets, magnetoelectric coupling at interfaces between ferromagnetic and ferroelectric materials, exchange bias at interfaces between antiferromagnetic and ferromagnetic materials and magnetically dead layers at interfaces between magnetic thin films and substrates. Since aberration corrected transmission electron microscopy inherently provides access to local structural and compositional information, the measured spin configurations will be correlated with local atomic arrangements, strain distributions, elemental diffusion, chemical bonding, charge transfer, orbital coupling and symmetry breaking at the atomic level. This combination of methods will contribute to a detailed fundamental understanding of the physical origins of the properties of magnetic materials at the atomic scale and will lead to new designs of magnetic materials for future applications with improved device functionality.