Modified magnetization and electron transition behavior in Bi2Fe4O9, Bi2Fe4O9-CoFe2O4 and Bi2Fe4O9-NiFe2O4

摘要

Mullite Bi2Fe4O9 (BFO) and its composites with spinel CoFe2O4 (CFO) and NiFe2O4 (NFO) have been synthesized by solid-state reaction, exhibiting visible-light response and enhanced ferromagnetic order simultaneously at room-temperature. Independent phases have been detected in composite samples by XRD, Raman spectroscopy and further confirmed by SEM images. Calculated through XRD patterns, it can be found that not only the lattice parameters and crystallite size, but also the growth preference orientation of BFO could be effected by spinel magnetic content. Optical spectroscopy shows three absorption edges existed which indicates multiple electron transitions for BFO and its composites. Interband electron transition occurs at 1.56, 0.92 and 0.47 eV for BFO, BFO-NFO and BFO-CFO respectively. Furthermore, M-H hysteresis loops suggest enhanced ferromagnetism in composite samples due to magnetic spinel CFO and NFO phase. Different curve shape and remnant magnetization imply the different intrinsic magnetic nature of CFO and NFO.