Self-purifying La2/3Sr1/3MnO3 epitaxial films: observation of surface precipitation of Mn3O4 particles for excess Mn ratios

Více o knize

20-25 nm thin films based on La2=3Sr1=3MnO3 (LSMO) are created using an Oxide Molecular Beam Epitaxy (MBE) setup. Various effusion cell shutter opening intervals are employed for sample production in co-deposition and shuttered modes. In-situ Reflection High-Energy Electron Diffraction (RHEED) intensity measurements reveal distinct oscillations, indicating layer stacking with stoichiometry influenced by shutter opening times, particularly concerning La2=3Sr1=3O and MnO content. The films exhibit vertical stoichiometric constant and gradient structures. Low Energy Electron Diffraction (LEED) and X-Ray Diffraction (XRD) confirm the expected Bragg reflections for epitaxial growth. XRR analysis aligns with the nominal layer thickness and composition. To assess magnetic layer thickness and potential magnetic gradients, Polarized Neutron Reflectometry (PNR) measurements are conducted. However, the depth-dependent magnetization behavior does not match anticipated structures. A refined model incorporating MnOx excess near the surfaces is required for scattering length density. High-Resolution Transmission Electron Microscopy (HRTEM) images reveal homogeneous perovskite LSMO layers with MnOx precipitates, identified through SQUID measurements as having Mn3O4 stoichiometry. The combination of experimental methods highlights discrepancies between nominal and actual layer compositions, showing LSMO's preference for growth in pure La2=3Sr1