Scanning Electron Microscopy with Polarization Analysis: Studies of Magnetic Microstructure

Abstract

When a beam of electrons with energies greater than several hundred eV is incident upon a ferromagnetic metal, spin polarized secondary electrons are emitted. The polarization of these secondary electrons is related to the polarization of the electrons in the ferromagnet. In the case of transition metal ferromagnets, the polarization of the secondary electrons is directly proportional to the magnetization. Spin polarization analysis of the secondary electrons, therefore, provides a direct measurement of the magnetization in the region probed by the incident electron beam. Scanning electron microscopy with polarization analysis (SEMPA), illustrated schematically in Fig. 11.1, combines the finely focused beam of the scanning electron microscope with secondary electron spin polarization analysis to obtain a technique that provides high resolution images of the surface magnetic microstructure of ferromagnetic materials. The purpose of this chapter is to review the SEMPA technique and to present several examples of magnetic microstructures that were studied using SEMPA.