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SUMMARY:Measurement of local magnetic properties of devices  with transmis
 sion electron microscopy - Xiaoxiao Fu\, CEMES-CNRS\, Toulouse\, France
DTSTART:20160622T130000Z
DTEND:20160622T140000Z
UID:TALK66643@talks.cam.ac.uk
CONTACT:Duncan Johnstone
DESCRIPTION:Energy-loss magnetic chiral dichroism (EMCD)\, which was exper
 imentally realized by P. Schattschneider et al. for the first time in 2006
 \, is a technique based on electron energy-loss spectroscopy (EELS). It ai
 ms at measuring the element-specific local magnetic moment of solids at a 
 nanometer scale. Compared to its analogue X-ray magnetic circular dichrois
 m (XMCD)\, EMCD has its potential advantage in spatial resolution. In rece
 nt years\, EMCD studies of 3d transition metal atoms or ions in cubic crys
 tals have been extensively performed\, and its experimental setups\, data 
 processing methods as well as the application of sum rules have been const
 antly improved. With promising prospects\, EMCD is still on its way to be 
 a routine magnetic characterization technique. It is of importance to appl
 y this technique to different groups of elements and crystal systems\, for
  investigating its sensitivity in different cases and further extending it
 s applications. \n\nIn this talk\, I will present the EMCD studies of epit
 axial MnAs thin films grown on a GaAs(001) substrate and DyFe2/YFe2 superl
 attices. The 3d orbital-to-spin moment ratio of Mn in hexagonal ferromagne
 tic MnAs along easy\, hard and intermediate magnetic axes was estimated by
  EMCD. Moreover\, a breaking of the ferromagnetic order in MnAs thin film\
 , together with the crystallographic transition from hexagonal α-MnAs to 
 quasi-hexagonal β-MnAs\, was locally observed in-situ by modifying the te
 mperature of the crystal inside the electron microscope. In addition\, I w
 ill show a simultaneous probe of 3d and 4f moments by investigating Fe-L2\
 ,3 and Dy-M4\,5 edges in DyFe2/YFe2 superlattices. EMCD signals of both Fe
  and Dy were observed. Sum rules exclusively for M4\,5 edges were derived.
  The antiparallel alignment of net Dy and Fe moments was confirmed\, takin
 g into account the dynamic diffraction effects. The work illustrates for t
 he first time the feasibility of EMCD technique for quantitative study of 
 magnetocrystalline anisotropy and magnetic transition\, and also proves it
 s potential as a tool to investigate 4f moment as well as moment coupling 
 in magnetic materials. 
LOCATION:LT Goldsmith 1 Materials Science and Metallurgy\, Department of
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