Photoinduced Electron Spin Resonance Phenomenon in α-Cr2O3 Nanospheres

The photoinduced phenomenon in alpha-Cr2O3 nanoscaled spherical particles was investigated in the temperature range of 150 up to 315K. An X-band electron-spin resonance spectrometry was employed to probe the magnetic behavior in alpha-Cr2O3 under an IR illumination in the nanosecond regime. The photoinduced effect on both low and high field ESR signals appears above 280K and is remarkably enhanced just below Neel temperature T-N. Such a photoinduced ESR phenomenon disappears in a reproducible way in the paramagnetic insulating state which occurs above T-N of crystalline alpha-Cr2O3. In the antiferromagnetic phase, that is, below T-N, the shift of the low field absorption could be attributed to the interaction of the light with specific Cr3+ ions located in strongly distorted sites correlated to strong ligand-field effect.