Magnetism observation by using synchrotron radiation: magnetic dichroism/photoelectron spectromicroscope

Magnetic domain observation methods using synchrotron radiation light are reviewed. As compared with the other microscopic methods such as magnetic force microscope, Kerr microscope, spin-polarized SEM etc., the imaging methods using synchrotron radiation give us several advantages. The most important advantage is the element specificity coming from the energy tenability to the atomic core levels of the probing light. In order to image such element specific magnetic imaging, magnetic circular and linear dichroism (MCD and MLD) effects are combined with microscopy methods. Depending on relative direction between the helicity of the incident light and the magnetic moment of observed area of the sample, the cross section of the absorption or photoemission spectra are different in MCD effect. The effect is especially dominated at the absorption edge of magnetic elements, thus element specific magnetic imaging becomes possible. In MLD, depending on the relative direction between the polarization vector of the light and magnetic moments, the cross section changes. The MLD effect is observed not only for ferromagnetic materials but also antiferromagnetic materials. This enables us to make antiferromagnetic domain imaging. In order to achieve such microscopy, there are several setups for the imaging techniques. One is to focus the synchrotron radiation beam to nano-micron meter size by using some optical elements. Another is to magnify photoelectron image from samples by using electrostatic and/or magnetic lens systems. Especially, the photoemission electron microscope system (PEEM) is now commercially available and widely used in many synchrotron radiation facilities. Recently, combination method of such microscopy and pump and probe technique becomes possible and gives us very interesting results of dynamical information of domain motion. Some examples by these techniques are introduced. (author)