Apparatus and method for measuring magnetization of surfaces

Abstract

An optical apparatus and methods for efficiently determining the magnetization of a material at very high optical resolution are disclosed. Individual components of the magnetization may be determined. Components in the plane of the sample surface are imaged by illuminating the material obliquely with substantially parallel light of relatively high power and very well controlled uniformity and polarization, and using light scattered obliquely in a parallel beam in the opposite direction at the same angle as the angle of incidence to record an image. Reversing the illumination and observation directions allows subtraction of the two images and measurement of the magnetization in-plane. A second in-plane component orthogonal to the first, is obtained similarly after reorienting the plane of incidence 90 degrees. The third magnetization component,—perpendicular to the sample surface—, may be obtained using illumination at both angles of incidence and subtracting two images, each recorded when a light-polarization angle of offset from extinction, is reversed. All three components may thereby be imaged without recourse to modulating the sample magnetization as in previous methods. Magnetically 'hard' as well as 'soft' materials are measurable by these methods.