Detection of magnetic circular dichroism with subnanometer convergent electron beams
2016 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 13, 134430Article in journal (Refereed) Published
The electron energy-loss spectroscopy technique known as electron magnetic circular dichroism (EMCD) has enormous potential for quantitatively probing the magnetic behavior of materials on the nanoscale. However, the requirement for mostly parallel illumination conditions greatly complicates the extraction of EMCD signals from surface areas under a few square nanometers, because scanning probe methods are limited to around this spatial resolution by the need for higher convergence angles. Here we propose theoretically and demonstrate experimentally that EMCD detection is feasible with convergence angles that are sufficiently large even for atomic resolution spectroscopy. Utilizing scanning transmission electron microscopy we experimentally detect a clear EMCD signal from a 50-nm-thick sample of bcc iron using a convergence semiangle of 8 mrad at 300 keV acceleration voltage, resulting in a probe size of approximately 2 angstrom. We subsequently estimate the number of chirally scattered electrons needed for an unambiguous detection of the EMCD signal and present a method to quantify confidence in signal detection.
Place, publisher, year, edition, pages
2016. Vol. 94, no 13, 134430
Condensed Matter Physics Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-308916DOI: 10.1103/PhysRevB.94.134430ISI: 000387015900003OAI: oai:DiVA.org:uu-308916DiVA: diva2:1051182
FunderSwedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2009-2017