Light-induced ESR in polycrystalline and thin films of Cr2O3

We studied on a chromium oxide Cr2O3 to investigate near-infrared (NIR) light-induced magnetism function at room temperature. A X-band electron-spin resonance (ESR) spectrometer and a SQUID magnetometer were employed to clarify magnetic behavior in the Cr2O3 under the illumination of NIR light (gimel = 1064nm). The light-induced ESR signal appears above 250K and is remarkably enhanced around room temperature. Contrary, with visible green light (gimel = 532nm), the ESR profile does not show any change. The light-induced ESR is strongly dependent on the irradiation light wavelength. We conclude the light-induced ESR below T-N may come from light-excited carriers associating with a reentrance from anti ferromagnetic to paramagnetic spin order. Thin films were successfully prepared by a RF magnetron sputtering and a sol-gel method. The T-N of the thin film is increased from 308 to about 400 K. We discuss intriguing properties on light-induced effect for both polycrystalline and thin films and state the chromate is a candidature to be applied to NIR detection industrial devices. (c) 2006 Elsevier B.V. All rights reserved.