Resonant photoemission and X-ray absorption spectroscopies of lithiated magnetite thin film

Abstract

Resonant photoemission spectroscopy (RPES) and X-ray absorption spectroscopy (XAS) were used to investigate the effect of lithiation on the electronic structure of Fe 3 O 4 thin film relevant to the operation mechanism of nanoionic devices to enable magnetic property tuning. Comparison of the Fe 2p XAS spectrum for lithiated Fe 3 O 4 (Li-Fe 3 O 4 ) with that for pristine Fe 3 O 4 clearly demonstrated that the number of Fe 2+ ions at octahedral B sites is increased by lithiation. The valence band RPES spectra of Li-Fe 3 O 4 further showed that lithiation increases the density of states near the Fermi level originating Fe 2+ ions at octahedral B sites. These findings agree well with the observed decrease in the saturation magnetization in the magnetization-magnetic field (M-H) loop of Li-Fe 3 O 4 thin film, indicating that minority spins (down spins) increase (i.e., total spins decrease) due to lithiation. The variation in the number of Fe 2+ ions at B sites is suggested to be an underlying operating mechanism of a nanoionics-based magnetic property tuning device.

Surface Defect Chemistry and Electronic Structure of Pr0.1Ce0.9O2−δ Revealed in Operando

“…Figure b shows that the on-resonance VB spectra showed an intensity much higher than that of off-resonance VB spectra, regardless of the applied bias. This enhanced intensity proves the existence of Pr 4f states near the Fermi level, − consistent with earlier results reported in ref . Taking a closer look at the line shape of the on-resonance data, we found that while there were no appreciable changes in on-resonance VB spectra at the Pr 3+ XAS maximum, clear changes in VB shapes as a function of applied bias were observed for spectra excited at the Pr 4+ absorption maximum, shown in Figure c.…”