We studied on a chromium oxide Cr₂O₃ to investigate near-infrared (NIR) light-induced magnetism function at room temperature. It is well known that the Cr₂O₃ has a corundum crystal structure with antiferromagnetic (AF) transition at T_N ~ 308 K. 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 (λ = 1064 nm). Under the light illumination, the light-induced ESR signal appears above 250 K and is remarkably enhanced around room temperature. Contrary, with visible green light (λ = 532 nm), the ESR profile does not show any change. The light-induced effect 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 antiferromagnetic 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 was increased from 308 K 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.

Keywords: light-induced magnetism, Perovskite structure, Spin State transition, ESR

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