Spin-orbit entanglement in Mn3+ indduced by the Jahn-Teller effect

In recent years, we have explored spin-orbit entanglement in Mn³⁺ ions, driven by the Jahn-Teller effect. This entanglement arises due to the reduction of the energy gap (S) between high- and low-spin configurations of Mn³⁺ ions in the presence of correlated Jahn-Teller polarons. Our investigation, using magneto-optical spectroscopy on La₂/₃Ca₁/₃MnO₃ thin films, has revealed an enhanced signal near the ferromagnetic transition temperature (TC = 260 K), where correlated polarons emerge. Additionally, we confirmed the gap reduction by analyzing the pre-edge features of O K-edge X-ray absorption spectroscopy (XAS) spectra, obtained at the BOREAS beamline in 2024. These spectra show a distinct gap reduction coinciding with the onset of the ferromagnetic transition. To further substantiate our findings, we plan to perform O K-edge XAS measurements on La₀.8Ca₀.2MnO₃ thin films, which exhibit a shifted ferromagnetic transition at TC = 215 K. The anticipated results, showing a similar gap reduction at a lower temperature, are expected to provide crucial evidence of spin-orbit entanglement in 3d ions. This would offer significant insights into the physics of electronically correlated systems, where orbital, spin, and lattice degrees of freedom are intricately connected.