Measuring magnetism in 3D
A team of researchers from Uppsala University, China and Germany has substantially extended the possibilities of an experimental technique called EMCD, that is used for measuring magnetism in materials. The results were published in Nature Communications on May 15 2017.
The EMCD (electron magnetic circular/chiral dichroism) method uses a transmission electron microscope to analyse, how electrons scatter on magnetic materials. Physical processes involved in EMCD are very similar as in XMCD, (x-ray magnetic circular dichroism), which is a well-established experimental method for precise measurements of magnetism. XMCD measures absorption of x-rays in magnetic materials, generated in synchrotrons, such as the unique instrument in MAX Lab IV in Lund.
According to previous theoretical research at Uppsala University from 2011 it was shown that EMCD should be sensitive not only to magnitude of the magnetization, but also to all three components of the magnetization vector. Now the research team have detected signals from the EMCD method originating from magnetization of cobalt in a direction perpendicular to the electron beam, not just a projection of magnetization vector to the beam direction, which is a limitation of the XMCD method that can only detect magnetization parallel to the x-ray beam. Another advantage of the EMCD method is its capability to provide magnetic information from very small areas, reaching sub-nanometer level.
The new results open paths for development of efficient high-spatial resolution magnetic measurement methods, capable of measuring all three components of the magnetization vector, to obtain the complete magnetization vector field.
Dongsheng Song, Amir H. Tavabi, Zi-An Li, András Kovács, Ján Rusz, Wenting Huang, Gunther Richter, Rafal E. Dunin-Borkowski, Jing Zhu, An in-plane magnetic chiral dichroism approach for measurement of intrinsic magnetic signals using transmitted electrons, Nature Communications 8, 15348 (2017), http://dx.doi.org/10.1038/ncomms15348
Ján Rusz, Stefano Rubino, Olle Eriksson, Peter M. Oppeneer, Klaus Leifer, Local electronic structure information contained in energy-filtered diffraction patterns, Phys. Rev. B 84, 064444 (2011), http://dx.doi.org/10.1103/PhysRevB.84.064444