Magnetic imaging with full-field soft X-ray microscopy

The current achievements in magnetic transmission soft X-ray microscopy are reviewed. The magnetic contrast is given by X-ray magnetic circular dichroism (X-MCD), i. e., the dependence of the absorption coefficient of circularly polarized X-rays on the projection of the magnetization in a ferromagnetic system onto the photon propagation direction. X-MCD contrast can reach, e. g., at L_2,3 edges in transition metals large values up to 50 %. Combined with a soft X-ray microscope where Fresnel zone plates as optical elements provide a lateral resolution down to 25 nm, it allows for imaging magnetic microstructures. Recording the images in varying external magnetic fields, inherent chemical specificity, a high sensitivity to thin magnetic layers due to the large contrast, and the possibility to distinguish between in-plane and out-of plane contributions allow detailed studies of static magnetization reversal processes in magnetic patterned elements and thin films. Micromagnetic simulations support the experimental findings. The broad applicability of this novel experimental technique to both fundamental and technologically relevant issues in nanomagnetism is demonstrated by selected examples. Future directions towards imaging spin dynamics on a psec time scale are briefly outlined.