Insight into the Electronic Phase Separation in Perovskite Manganites: The Role of Charge-Orbital Ordering in the Interface Region*

The electronic phase separation in perovskite manganites, with coexistence of ferromagnetic (FM) metallic and antiferromagnetic (AFM) insulating phase, provides possibilities for tuning their electronic and transport properties. However, the mechanisms that drive the electronic phase separation are still unclear. Using density functional theory calculations, we investigated the charge-orbital ordering (COO) in both the AFM and FM/AFM interface regions of La_1-xSr_xMnO3 (LSMO). We found that the interface region prefers a distinct COO phase compared with the AFM region, which facilitates the formation of FM/AFM domain boundaries. We further studied the thickness dependent COO phase transition in LSMO ultrathin film, and predicted its critical thickness of phase separation. The results are in well agreement with experiments. These findings suggest that the COO phase transition in the FM/AFM interface region plays a key role in the electronic phase separation. The influence of substrate strain and Sr doping level on the phase separation were also studied.