(a) Mn valence changes at the series of La_1−xSr_xMnO₃/SrTiO₃ interfaces. Spectroscopic images are shown for x = 0, 0.1, 0.2, 0.3, and 0.5 films (from left to right), where Ti is plotted in blue, Mn in green, and La in red, and the x = 0.5 image shows cation ordering not observed in other films. (b) Three Mn reference spectra for Mn⁺², Mn⁺³, and Mn^+3.5, used to determine the Mn valence across the interface. (c) The results of the non-negative non-linear least squares fit of the components in panel (b) for x = 0, 0.1, 0.2, 0.3, and 0.5 (from left to right). Error bars plot the standard error of the mean generated from five binned regions from each spectroscopic image. Scale bar is 1 nm. Reproduced from Ref. [46].