Young's Double Slit Interference with Circularly Polarized Soft X-Ray Photons

We demonstrate a proof-of-concept hybrid spectroscopic-interferometric technique that introduces a novel experimental method to quantify magneto-optical effects. The technique combines x-ray magnetic circular dichroism (XMCD) with x-ray interferometry, adapting the concept of Young’s double-slit experiment. Specifically, by applying a magnetic thin film over one slit and utilizing XMCD, we demonstrate the capability to determine both the real (β) and the imaginary (δ) parts of the complex magnetic refractive index n (n = 1 - δ + iβ) from the resulting interference fringes. We track the shift of the fringes of the interference pattern that arise from changes in the sample's magnetization. This methodology offers a direct means to probe variations in the magnetic refractive index as a function of the electron spin moment. Our technique, which can act as a magnetometer, significantly optimizes the determination of fundamental magneto-optical parameters using soft x-rays with high sensitivity and simplicity.