Magnetic contrast in the scanning electron microscope

Abstract

An analysis of secondary electron magnetic contrast is presented. The analysis is based upon a simple cylindrically symmetric model for the fringing fields of materials. It is carried to the point of predicting "optimum" secondary electron collection and describes two quantitative field measurement techniques. An analyzer was constructed for observing magnetic contrast in the SEM. It performs both a secondary electron energy discrimination function and a spatial aperturing function using diametrically opposing apertures. This type of analyzer has a potential signal-to-noise ratio about half that of "optimum" electron collection. Observations are made in this analyzer of various magnetic materials. Pictorial, semiquantitative, and quantitative results are described. Good field measurement correlations exist between the two techniques described and also between them and the "expected" values. © 1971 The American Institute of Physics.