Figure 8
Atomic-scale STEM image visualizing the cooperative Jahn–Teller effect (CJTE); the STEM EELS shows the Mn charge ordering. (a) Mn EELS L3/L2 peak ratio at each Mn [010] atomic column site along the STEM-EELS scanning direction of [100]; the dashed lines show the ratios that correspond to the standard MnO2 and Mn2O3 samples. Error bars are determined from the errors introduced from background subtraction and data fluctuation among spectra. (b) STEM image along the [010] zone axis shows the periodic distortion of the Mn ab plane and the intensity modulation of the Na plane, a result quantitatively consistent with the superstructure model in the inset (the Nadisp ball indicates Na ions displaced by <0.5 Å from their original lattice position). (c) 17 Mn L2,3-edge EEL spectra after background subtraction that provide the L3/L2 ratios shown in (b). Reproduced with permission.68
