DOE OSTI · 2525844
Topotactic Reduction‐Driven Crystal Field Excitations in Brownmillerite Manganite Thin Films
Abstract
Topotactic reduction of perovskite oxides offers a powerful approach for discovering novel phenomena, such as superconducting infinite-layer nickelates and polar metallicity, and is commonly accompanied by the emergence of multiple valence states and/or complex crystal fields of transition metals. However, understanding the complex interplay between crystal chemistry, electronic structure, and physical properties at the spin- and orbital-resolved levels in these reduced systems remains elusive. Here, in this study, x-ray absorption spectroscopy, resonant inelastic x-ray scattering (RIXS), and density functional theory calculations are used to uncover topotactic metal-insulator transition and orbital-specific crystal field excitations in brownmillerite La 0.67 Ca 0.33 MnO 2.5 thin films. The Mn valence states are found to be Mn 2+ /Mn 3+ , along with their corresponding populations at octahedral and tetrahedral sites, which effectively weaken the Mn-O hybridization compared to the parent perovskite phase. As a result, La 0.67 Ca 0.33 MnO 2.5 films exhibit an antiferromagnetic insulating ground state. Moreover, by combining the RIXS measurements on selected single-valence manganites, specifically MnO, LaMnO 3 , and CaMnO 3 , with orbital- and spin-resolved density-of-states calculations, the study identifies the dd excitations of octahedrally and tetrahedrally coordinated Mn 2+ /Mn 3+ ions, directly linking the microscopic electronic structure to the macroscopic magnetic/electrical properties.
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Jin, Feng [University of Science and Technology of China, Hefei (China)] (ORCID:0000000256880364), Fan, Shiyu [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Gu, Mingqiang [Southern University of Science and Technology (SUSTech), Shenzhen (China); Sun Yat‐sen University, Shenzhen (China)], Lv, Qiming [University of Science and Technology of China, Hefei (China)], Ge, Min [University of Science and Technology of China, Hefei (China)], Zhang, Zixun [University of Science and Technology of China, Hefei (China)], Zhang, Jinfeng [University of Science and Technology of China, Hefei (China)], Lu, Jingdi [University of Science and Technology of China, Hefei (China)], Kim, Taehun [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Bhartiya, Vivek [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Huang, Zhen [Anhui University, Hefei (China)], Wang, Lingfei [University of Science and Technology of China, Hefei (China)], Bisogni, Valentina [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Pelliciari, Jonathan [Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)], Wu, Wenbin [University of Science and Technology of China, Hefei (China); Anhui University, Hefei (China); Chinese Academy of Sciences (CAS), Hefei (China)]. 2025-02-19. Topotactic Reduction‐Driven Crystal Field Excitations in Brownmillerite Manganite Thin Films. https://doi.org/10.1002/adfm.202501893
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