Improved magnetic domain imaging in photoelectron emission microscopy using symmetry analysis and momentum selection

Magnetic circular dichroism in photoemission provides a powerful tool for probing the electronic and magnetic structure of ferromagnets. In the threshold regime, the use of laboratory light sources enables magnetic domain imaging with photoelectron emission microscopy (PEEM), but the achievable magnetic contrast is typically weak, leading to long acquisition times. In this work, we present a theoretical study of contrast enhancement in threshold-photoemission PEEM based on symmetry considerations and relativistic one-step photoemission calculations. We show that surface symmetry imposes specific relations among the fundamental dichroic intensities and the corresponding asymmetries, which can be exploited by momentum selection using an aperture in the PEEM. As a prototype system, we investigate in-plane and perpendicular magnetized Fe(001). Our results demonstrate that sizable magnetic domain contrast can be achieved at low photon energies by selecting appropriate emission directions, providing a practical route toward efficient laboratory-based magnetic domain imaging. • Large asymmetry values of the exchange contribution. • Sign and value depend on the k-region. • Shape of emission pattern reflects symmetry of surface.