Prospect for detecting magnetism in two-dimensional perovskite oxides by electron magnetic circular dichroism

Abstract

Two-dimensional (2D) magnets, especially strongly correlated 2D transition-metal perovskite oxides, have attracted significant attention due to their intriguing electromagnetic properties for potential applications in spintronic devices. Potentially electron magnetic circular dichroism (EMCD) under zone axis conditions can provide three-dimensional components of magnetic moments in 2D materials, but the collection efficiency and the signal-to-noise ratio for out-of-plane (OOP) components is limited due to the limited collection angle. Here we conducted a comprehensive computational simulation to optimize the experimental setting of EMCD for detecting the OOP components of magnetic moments in three beam conditions (3BCs) on 2D perovskite oxides La_1-xSr_xMnO₃ (LSMO) in a TEM. The key parameters are sample thickness, accelerating voltage, Sr doping concentration, collection semi-angle and position, and sample orientation including systematic reflections excited and tilt angle. Our simulation results demonstrate that the relative dynamical diffraction coefficients of Mn OOP EMCD of LaMnO₃ with a thickness ranging from 1 unit cell (uc) to 4 uc can be optimized in a 3BC with (110) systematic reflections excited and a relatively large collection semi-angle of 19 mrad at the relatively low accelerating voltage of 80 kV. In most cases, the relative dynamic diffraction coefficients for La_1-xSr_xMnO₃ with the thickness ranging from 1 uc to 4 uc decrease with the increase of the Sr doping concentrations. The optimal tilt angle from a zone axis to a 3BC is 18° for the cases of the LSMO thickness of 2 uc, 3 uc and 4 uc, and 22° for the monolayer LSMO. Our work provides the theoretical simulation foundation for optimized EMCD experiments for measuring OOP components of magnetic moments in 2D transition-metal perovskite oxides.