Defect-Controlled Magnetism: Elucidating, via PDF, the Origin of Large Exchange Bias in Cobalt-Doped Iron Oxide Nanoparticles

Iron-oxide based magnetic particles (MNPs) play a crucial role in various technological and medical applications. Here, we propose the use of high energy x-ray diffraction to obtain pair distribution function (PDF) information related to aspects of the intraparticle crystallinity along a series of cobalt-doped iron oxide MNPs. This unique structural information will allow us to address the origin of exceptionally high exchange bias properties observed in the series, emergent upon increasing Co doping. In particular, we will determine the type of defective structures generated upon Co doping. Together with preliminary information available from high resolution electron microscopy studies and details on stoichiometry, valence, and local coordination, which will be obtained by XANES and EXAFS spectroscopies, the proposed application of the synchrotron x-ray based PDF technique will allow a comprehensive study on the structure-magnetic relationship in these applications-relevant materials.