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Surface spin canting in F e3 O4 and CoF e2 O4 nanoparticles probed by high-resolution electron energy loss spectroscopy
, H. Sharona, U. Bhat, S. Palchoudhury, A. Gupta, R. Datta
Published in American Physical Society
2017
Volume: 95
   
Issue: 17
Abstract
High-resolution electron energy loss spectroscopy (HR-EELS) is utilized to probe the surface spin canting in nanoparticles of two technologically important magnetic materials, i.e. Fe3O4 and CoFe2O4 (CFO). A soft experimental technique has been developed that is capable of extracting EELS spectra with single atomic plane resolution recorded in a single frame. The technique yields information at different depths of the nanoparticle from the surface to the core regions with high signal-to-noise ratio and without beam damage. This enables comparing the fine structures between the surface and core regions of the nanoparticles. The results confirm earlier observations of uniformly oriented spin canting structure for CFO and provide additional information regarding atom site-selective spin canting information. In the case of Fe3O4, preferred canting orientation forming core and shell structure is deduced. Unlike earlier reports based on polarized spin-flip neutron scattering measurement, it is possible from the experimental spectra combined with the first principle-based calculations considering noncollinear magnetism to narrow down the canting angles for Fe3O4 (Td,Oh tilts 40°, 40°) and CFO (Td,Oh tilts 17°, 17°). In addition, the role of Dzyaloshinskii-Moriya interaction in stabilizing the spin canting at the nanoparticle surface is discussed. The results demonstrate that HR-EELS can be a powerful technique to probe the magnetic structure in nanodimensional systems and has advantages over neutron-based techniques in terms of superior spatial resolution, site-specific information, and ease of sample preparation. © 2017 American Physical Society.
About the journal
JournalData powered by TypesetPhysical Review B
PublisherData powered by TypesetAmerican Physical Society
ISSN24699950