Soft x-ray circular polarizer using magnetic circular dichroism at the Fe L3 line

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Abstract
Linearly polarized soft x-rays are converted to elliptical polarization at the Fe L3 line (707 eV) using magnetic circular dichroism (MCD) on transmission through thin Fe films. A linear polarizer measured the transmitted polarization at different incidence angles to vary as expected from a model for in-plane magnetization, and also to exhibit a weak MCD effect at normal incidence interpreted to originate from perpendicular interface anisotropy. An MCD signal from a downstream Fe film was produced by switching the helicity of x-rays transmitted through an upstream circular polarizer. Practical considerations for optimizing the production of circular polarization are discussed, and synchrotron radiation applications using these circular polarizing filters are suggested.