Synthesis and Room Temperature d0 Ferromagnetic Properties of α-MoO3 Nanofibers

Herein, we report the magnetic properties of α-MoO3 nanofibers synthesized via a hydrothermal method. X-ray photoelectron and Raman spectroscopic studies have been employed to evidence the presence of oxygen vacancy defects in the α-MoO3 nanofibers. To elucidate the oxygen vacancy related ferromagnetism, post-thermal annealing in oxygen and vacuum was performed. The UV emission band of α-MoO3 nanofibers reveals a red shift from oxygen annealed to vacuum annealed, indicating a band-edge reduction. The saturation magnetization of oxygen annealed nanofibers decreases while that of vacuum annealed nanofibers increases. These results strongly confirm that the oxygen vacancies play a significant role in inducing ferromagnetism. The origin of ferromagnetism may be due to the exchange interactions among localized electron spin moments resulting from oxygen vacancies of α-MoO3 nanofibers. The presence of such defects was further supported by the photoluminescence measurements.