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UID:DSC-8940
DTSTART;TZID=Europe/Berlin:20150311T140000
SEQUENCE:1426059604
TRANSP:OPAQUE
DTEND;TZID=Europe/Berlin:20150311T150000
URL:https://www.dresden-science-calendar.de/calendar/de/detail/8940
LOCATION:IFW\, Helmholtzstraße 2001069 Dresden
SUMMARY:Rusz: Towards measurement of magnetic properties of single atomic c
 olumns
CLASS:PUBLIC
DESCRIPTION:Speaker: Dr. Jan Rusz\nInstitute of Speaker: Department of Phys
 ics and Astronomy\, Uppsala University\, Sweden\nTopics:\nMaterialien\, Ph
 ysik\n Location:\n  Name: IFW (D2E.27\, IFW Dresden)\n  Street: Helmholtzs
 traße 20\n  City: 01069 Dresden\n  Phone: \n  Fax: \nDescription: Achievi
 ng quantitative measurements of bulk magnetic properties with atomic later
 al resolution is one of the great promises of modern aberration-corrected 
 scanning transmission electron microscopes. The principle that allows meas
 uring magnetism in an electron microscope is based on electron magnetic ci
 rcular dichroism (EMCD\; [1])\, an electron analogue of the established x-
 ray magnetic circular dichroism. It is expected that with electron vortex 
 beams [2] it should be possible to measure EMCD at an atomic resolution [3
 ]\, although forming atomic sized vortices remains a challenge. The most p
 romising approaches are based on magnetized needles [4\,5] or utilizing ad
 ditional lens for magnifying the beam split by a fork aperture [6\,7]\, se
 lecting the desired vortex with a slit and demagnifying it back [8].  An a
 lternative approach\, which does not require specialized apertures and uti
 lizes the whole electron beam intensity\, is based on tuning the k-space p
 hase distribution of the beam to the symmetry of underlying crystal [9]. F
 or example\, for cubic or tetragonal crystals one could set the four-fold 
 astigmatism to a nonzero value (few tens of micrometers)\, while keeping t
 he other aberrations as low as possible. Such approach can be implemented 
 into any probe-corrected STEM\, which offers the flexibility to independen
 tly tune individual aberrations to desired nonzero values.  We will overvi
 ew the theoretical principles behind atomic resolution magnetic measuremen
 ts and present measurements with atomic-sized aberrated beams on an antife
 rromagnetic compound LaMnAsO [10].  [1] P. Schattschneider et al.\, Nature
  441\, 486 (2006). [2] M. Uchida and A. Tonomura\, Nature 464\, 737 (2010)
 . [3] J. Rusz\, S. Bhowmick\, Phys. Rev. Lett. 111\, 105504 (2013). [4] A.
  M. Blackburn\, J. C. Loudon\, Ultramicroscopy 136\, 127-143 (2013). [5] A
 . Beche et al.\, Nat. Phys. 10\, 26 (2014). [6] B. McMorran et al.\, Scien
 ce 331\, 192 (2011). [7] J. Verbeeck\, H. Tian\, and P. Schattschneider\, 
 Nature 467\, 301 (2010). [8] O. L. Krivanek et al.\, Microscopy and Microa
 nalysis 20\, 832 (2014). [9] J. Rusz\, J. C. Idrobo\, S. Bhowmick\, Phys. 
 Rev. Lett. 113\, 145501 (2014). [10] J. C. Idrobo et al.\, submitted.
DTSTAMP:20260615T072810Z
CREATED:20150304T075346Z
LAST-MODIFIED:20150311T074004Z
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