Soft x-ray studies of nanomagnetic and spintronic materials at Brookhaven National Laboratory

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The Leeds Condensed Matter Physics Group have been regular users of synchrotron radiation at the NSLS now for over six years, where the unique element-specific sensitivity to magnetism of polarized soft x-rays has made great contributions to our research in studying disorder, anisotropy and hysteresis in a variety of nanomagnetic systems. Here we request travel funding to allow us to pursue here two main avenues of research in our new two year user programme at that facility. The first is soft x-ray magnetic scattering from arrays of nanomagnets, fabricated at the Brookhaven Center for Functional Nanomaterials, which exhibit frustrated geometries: whilst the underlying physical structure is periodic, the magnetic structure will display only short range order due to the frustration. Off-specular magnetic scattering will allow us to characterize this disorder as a function of sample array geometry, magnetic field, and temperature, yielding complementary information to real space imaging techniques. The second area is in the study of magnetic nanoclusters, formed by gas-phase aggregation and deposited as part of a magnetic multilayer stack such as a tunnel junction. We have the capability to produce very narrow and well-controlled size distributions, so size dependences. Here we will study spin-orbit moment ratios and chemical composition, such as oxidation from surrounding tunnel barrier material, using XMCD spectroscopy. Unlike similar european facilities, synchrotron beamtime at the NSLS does not come with money to support travel to the facility. The experiments form part of our ongoing and highly successful joint programme on magnetic scattering between Leeds and ISIS. The grant request is for travel and subsistence funds only to allow a team of three people to travel to Brookhaven for five weeklong periods in order to operate the experiment 24 hours a day, as well as carry out sample fabrication at the CFN and present our results at conferences.