From the analysis of experimental X-ray absorption spectra and the calculation of atomic multiplets it is found that the grinding of powder manganites La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3 in a vibration mill results in the formation of nanocrystallites and a partial transformation of trivalent manganese ions into tetravalent. It is shown that in nanostructured manganite La0.5Ca0.5MnO3 the energy gap between the occupied and unoccupied states is absent. It os found that Mn2+ ions arise in Nd0.5Sr0.5MnO3 due to more intense deformation during the grinding.

Soft X-ray absorption (XAS) and emission (XES) spectroscopies were applied to determine valence states of manganese ions in nanostructured powder of halfdoped La0:5Ca0:5MnO3 manganite obtained by milling in a ball mill. XAS spectra were measured both in surfacesensitivity total electron-yield and in bulk-sensitivity total fluorescence-yield modes. O Ka XES and O 1s XAS spectra characterized the occupied and unoccupied partial O 2p densities of states are compared with band-structure calculations made using the TB-LMTO-ASA codes. Experimental Mn 2p, Ca 2p, and La 3d XAS spectra are compared with results of crystal field atomic multiplet calculations. For the nanostructured system of La0:5Ca0:5MnO3, concentrations of Mn4þ ions are found to be increased with increasing the time of milling.
DOI 10.1007/s00339-014-8774-8.