EPR spectra analysis of photo-magnetic properties of EuO nanocrystals

The temperature dependencies of magnetic susceptibility c of the europium oxide (EuO) nanocrystals were examined. The experimental Bohr magnetons (p) for EuO nanocrystals agreed well with the theoretical p for the 4f7 configuration (Eu(II)). A dramatic increase in magnetization of the EuO nanocrystals under UV irradiation at room temperature was observed by photo-magnetic measurements superconducting quantum interface device (SQUID with optical fiber). This increase in magnetization under UV irradiation can be explained by the occurrence of a d–f exchange interaction of conductive electrons in the 5d band (magnetic exciton). We suggest a mechanism in which the photo-magnetization increases by the presence of an exciton band in the UV region for the polyurea-modified EuO nanocrystals. In order to confirm the magnetic exciton of EuO nanocrystals, we carried out the electron paramagnetic resonance (EPR) measurements under UV irradiation, showing the formation of photo-active species in EuO nanocrystals.