Electronic structure of multiferroic TbMn2O5 probed by resonant x-ray inelastic scattering and x-ray absorption spectroscopy

Chen, J. M.; Lee, J. M.; Huang, S. W.; Shen, C. C.; Jarrige, I.; Ishii, H.; Cai, Y. Q.; Lu, K. T.; Yang, T. J.; Liang, K. S. Taiwan

The electronic structure and Mn valency of single-crystalline TbMn₂O₅ and polycrystalline Tb_1-xCa_xMnO₃ (x = 0 - 0.85) were investigated by x-ray absorption spectroscopy (XAS) (O K-edge and Mn K-edge) and resonant x-ray emission spectroscopy (RXES). The polarized O K-edge and Mn K-edge x-ray absorption spectra of TbMn₂O₅ single crystals show a strong polarization dependence along three crystallographic axes. The while line in Mn K-edge spectrum corresponding to the 1s to 4p transitions shows a lower energy for E // a polarization compared with E // b and E // c polarizations. The average Mn valency of TbMn₂O₅ along the a axis is less than that along the b and c axis. The 1s3p-RXES spectra of single-crystalline TbMn₂O₅ show that the fluorescence regime starts from the first pre-peak of 1s to 3d transitions, while the Raman regime is only limited to below the pre-edge. This provides clear evidence of the hybridization between Mn 3d orbitals and neighboring Mn 4p states in TbMn₂O₅, which leads to relatively delocalized intermediate states. The hybridization of Mn 3d and Mn 4p states is nearly isotropic along the a, b, and c axes of single-crystalline TbMn₂O₅. The absorption positions of Mn K-edge absorption spectra shift upward with increasing Ca content in Tb_1-xCa_xMnO₃. The spectral weight of pre-peaks at Mn K-edge increases with increasing Ca doping in Tb_1-xCa_xMnO₃ .

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