Oxygen partial-density-of-states change in theYBa2Cu3Oxcompounds forx≊6, 6.5, 7 measured by soft x-ray emission

We present oxygen K soft x-ray emission spectra for the ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathrm{x}}$ compounds with x nominally equal to 6, 6.5, and 7 and compare them with x-ray emission spectra determined from recent band-structure calculations. The K emission spectrum of O provides a measure of the p-type local partial density of states to (p-LPDOS) at the oxygen sites. As x decreases from 7-δ about 6.5, a chemical shift of the entire spectrum to lower energy indicates that screening is modified for all oxygen sites. The integrated intensity of the spectra is nearly unchanged by oxygen removal, indicating an increase in p-LPDOS per oxygen site. These results and changes in the spectral shape suggest that itinerant electron density near the O atoms is reduced and bound electron density is increased as oxygen is removed.