| With rapid progress in the fields of nanomagnetism, multiferroics and spintronics, amethod to characterize local magnetic structure information of the nanostructures is ofessential importance for understanding and designing the magnetic materials on ananometer scale. However, the (site-specific) magnetic structure determination from asmall region in complex materials is challenging.Electron energy loss magnetic chiral dichroism (EMCD)1technique was inventedrecently as a new route for detecting the magnetic signals using the transmitted electronbeam. By constructively applying the strong dynamical diffraction effects of fastelectrons,we develop a site-specific electron energy-loss magnetic chiral dichroism(site-specific EMCD) method to quantitatively solve magnetic structure in complexmaterials with non-equivalent crystallographic sites. We make major advances byadjusting dynamical diffraction conditions to enhance site-specific EMCD signals, andto extract site-specific magnetic chiral dichroism spectra in an example of NiFe2O4. Weachieve comprehensive magnetic structure information, including site-specific totalmagnetic moment and orbital to spin magnetic moment ratio, using site-specific EMCDmethod under assumption of no magnetic information available. The site-specific orbitalto spin magnetic moment ratios for octahedral Fe atom and tetrahedral Fe atom inNiFe2O4are for the first time experimentally obtained and reported in this work. Forthe first time, we experimentally demonstrate transmitted electron as a new source forquantitative magnetic structure determination. Compared with X-ray magnetic circulardichroism and neutron diffraction, site-specific EMCD shows its unique ability to solvethe site-specific magnetic structure of an object at a nanoscale level. The site-specificEMCD method opens a door for us totake challenge of exploring unknown magneticstructure information from a nanometer-scale region in complex magnetic materialsusing transmitted electrons. |
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