LaMnOにおける圧力下金属絶縁体転移のX線発光と吸収分光法の測定
Pressure-induced metal to insulator transition in LaMnO from X-ray absorption and emission spectroscopies
Jarrige, I.; Shieh, S.*; 石井 啓文*; 平岡 望*; Cai, Y.*
Jarrige, I.; Shieh, S.*; Ishii, Hirofumi*; Hiraoka, Nozomu*; Cai, Y.*
Here we report on a spectroscopic investigation of the intricate interplays between electronic, magnetic and structural properties of LaMnO across its pressure-induced insulator to metal transition (IMT) at 32 GPa. We measure the Mn K-beta fluorescence line by X-ray emission spectroscopy (XES) and the Mn K-egde by X-ray absorption spectroscopy in the partial fluorescence yield mode (PFY-XAS). The XES spectra disclose a high-spin to low-spin transition accompanying the IMT that points to strongly interwoven charge and spin degrees of freedom, which is reminiscent of the Mott perspective. On the other hand, close insight is gained on the structure from the Mn K pre-edge region, where evidence is found for a complete suppression of the Jahn-Teller distortions at the IMT. This is congruent with the scenario that the gap closure results from the progressive pressure-induced degeneracy of the majority-spin eg band, thus suggesting that the IMT in LaMnO is not a plain Mott transition.