Signal enhancement of electron magnetic circular dichroism by ultra-high-voltage TEM, toward quantitative nano-magnetism measurements.

Electron magnetic circular dichroism (EMCD) has been known as the transmission electron microscopy (TEM) counterpart of X-ray magnetic circular dichroism (XMCD). XMCD is already widely used for the characterization of magnetic materials with synchrotron radiation. There have been common difficulties encountered in quantitative analysis of the EMCD signal measured by medium-voltage TEMs, such as a small signal fraction and the low signal-to-noise ratio of the EMCD signal. Theoretical calculations of EMCD considering many-beam dynamical diffraction effects showed improved net magnetic signal fractions at an accelerating voltage of 1 MV compared with 200 kV, which is in agreement with the present experiment.