Fig. 4: Chemical environment study near db-PNRs.

a A plot of a line-scan EELS data across the db-PNR. The red and blue brackets on the right indicate the spectra from polar and non-polar regions, respectively. b The electron probe spatial locations superimposed on the ADF-STEM image. The red and blue brackets indicate the spectra from polar and non-polar regions, respectively. The color of the probe locations corresponds to the EELS spectra in a. c The averaged EELS Mn L edge spectra from the polar nanoregions (red) and non-polar matrix(blue), as indicated in a. The reference Mn²⁺ and Mn⁴⁺ spectra are also plotted as black solid and dashed lines. The height of the reference spectra is plotted based on the ELNES fitting results on both averaged spectra. d The plot of Mn²⁺ percentage versus the probe positions from the ELNES fitting results for the entire line-scan EELS data. The red and blue background colors indicate the polar and nonpolar regions, respectively. A spike in Mn²⁺ percentage is shown at the center of the polar region. e The EDX mapping near the db-PNR region. The approximate location of the db-PNR is pointed by the red arrows. The line profile of the EDX mapping intensity highlights the locally decreased and increased concentration of the Ca and Mn at db-PNR, respectively.