Photoemission and x-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)$_{3}$O$_{4}$ thin films exhibiting photo-induced magnetization

摘要

By means of photoemission and x-ray absorption spectroscopy, we have studiedthe electronic structure of (Ni,Zn,Fe,Ti)$_{3}$O$_{4}$ thin films, whichexhibits a cluster glass behavior with a spin-freezing temperature $T_f$ of$\sim 230$ K and photo-induced magnetization (PIM) below $T_f$. The Ni and Znions were found to be in the divalent states. Most of the Fe and Ti ions in thethin films were trivalent (Fe$^{3+}$) and tetravalent (Ti$^{4+}$),respectively. While Ti doping did not affect the valence states of the Ni andZn ions, a small amount of Fe$^{2+}$ ions increased with Ti concentration,consistent with the proposed charge-transfer mechanism of PIM.