6. Scanning electron microscopy with polarization analysis (SEMPA) and its applications

Abstract

Scanning electron microscopy with polarization analysis (SEMPA) is a technique for directly imaging the magnetic microstructure of surfaces and thin films. SEMPA relies on the fact that secondary electrons emitted from a magnetic sample in a scanning electron microscope (SEM) have a spin polarization, which reflects the net spin density in the material. This spin density, in turn, is directly related to the magnetization of the material. By measuring the secondary electron spin polarization, SEMPA can be used for the direct, high resolution imaging of the direction and the relative magnitude of a sample's magnetization, in the same way that a SEM can be used to image topography by measuring the secondary electron intensity. SEMPA is one of several methods used for imaging magnetic microstructure. This chapter reviews the technique and describes the types of magnetic imaging applications for which SEMPA is best suited. The origin of the magnetic contrast is described in the chapter as well as the instrumentation required for its measurement.