PNNL

Abstract

Disorder in Gd2Ti2O7 is investigated by near-edge x-ray absorption fine structure (NEXAFS) and x-ray photoelectron spectroscopy (XPS). NEXAFS shows Ti?4 ions occupy octahedral sites with a tetragonal distortion induced by vacant oxygen sites. O 1s XPS spectra obtained with a charge neutralization system from Gd2Ti2O7 (100) and the Gd2Ti2O7 pyrochlore used in Phys. Rev. Lett. 88, 105901 (2002), both yielded a single peak, unlike the previous result on the latter that found two peaks. The current results give no evidence for an anisotropic distribution of Ti and O. The extra features reported in the aforementioned communication resulted from charging effects and incomplete surface cleaning. Thus, a result confirming the direct observation of simultaneous cation–anion antisite disordering and lending credence to the split vacancy model has been clarified.