Surface- and bulk-sensitive x-ray absorption study of the valence states of Mn and Co ions in Zn1−2xMnxCoxO nanoparticles

Abstract

We have performed x-ray absorption spectroscopy (XAS) measurements on Zn1−2xMnxCoxO nanoparticles. From the XAS results, it seems that the Mn and Co ions are in a mixed-valence (2+, 3+, and 4+) state and the relative concentrations of the high-valence (3+ and 4+) Mn and Co ions are higher in the surface region than in the deep core region. We suggest that this is a distinct trend of nanoparticle diluted magnetic semiconductor (DMS) unlike the case of DMS in film and bulk forms, where the transition-metal ions are expected to be 2+.