Probing Changes In The Mn 3d Band Of Sm0.525sr0.475mno3 Induced By Oxygen Isotope Substitution

The oxygen-isotope effect on the low-temperature metal-insulator transition in Sm0.525Sr0.475MnO3 has been investigated using resonant inelastic x-ray scattering spectroscopy. The Mn L-3 x-ray emission spectra resonantly excited at L-3 threshold reveal a narrowing of the Mn d band in the O-18 containing Sm0.525Sr0.475MnO3 upon cooling down to 80 K. This d-band narrowing is absent in the O-16-containing sample. Overall the spectral behavior of Mn 3d band suggests that oxygen-isotope substitution increases the band gap of Sm0.525Sr0.475MnO3 and thus stabilizes the charge-ordered insulating phase of the O-18 containing Sm0.525Sr0.475MnO3 at low temperature.