Automatic Magneto-Optic Rotation Tester

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Abstract
An electromechanical device has been developed to measure quickly the angle of magneto-optic rotation of a light beam reflected from a thin film of metal. Various experimental arrangements for this purpose have been made in laboratories in the past; however, these have required laborious procedures on each sample that is to be tested and were somewhat inflexible. This paper describes an instrument constructed specifically for magneto-optic measurements, and also discusses some of the phenomena that can be examined by its use. The instrument alternately displays the light-output/analyzer-angle curves for the two magnetization states on an oscilloscope. The repetition rate is high enough that the two curves appear to be displayed simultaneously. (The longitudinal Kerr effect, which is the principle object of study here, provides rotations of less than 1.0° and typically on the order of 0.1°.) The time required to evaluate any film by visual observation of the scope traces with an accuracy of about 0.01° is approximately one minute, measurements to 0.005° can be made by using an oscilloscope camera.