Annealing effects on the ferromagnetism of Ce0.97Co0.03O2-delta compounds

作者：Song, Y. Q.^*; Zhang, H. W.; Liu, Y. L.; Li, Y. X.; Shah, L. R.; Xiao, John Q.

来源：Physica B: Condensed Matter , 2010, 405(11): 2530-2533.

DOI：10.1016/j.physb.2010.03.024

• Co doped CeO2
• Ferromagnetism
• F-center exchange mechanism
• Ar/H-2 annealing treatment

Diluted magnetic oxide of Ce0.97Co0.03O2-delta powder was synthesized by standard solid-state reaction method. Oxidized or reduced samples were obtained via O-2 or Ar/H-2 annealing, respectively. Magnetic investigations found that the as sintered Ce0.97Co0.03O2-delta is ferromagnetic at room temperature. The saturation magnetic moments (M-S) are highly enhanced by Ar/H-2 annealing, while sharply diminished by O-2 treatments. X-ray photoelectron spectroscopy (XPS) measurements show that Ce4+ ions are partially reduced to Ce3+ with additional oxygen vacancies (V-O) being introduced by Ar/H-2 annealing. The increase of V-O by Ar/H-2 annealing is further proved by Raman spectra in which a new Raman scattering peak appearing at the frequency of 465 cm(-1). This fact contributes to the enhanced ferromagnetism observed in reduced Ce0.97Co0.03O2-delta. On the other hand, V-O density is reduced via O-2 annealing and thus leading to a decreased M-S. On all accounts M-S is found to be in direct ratio-dependent on V-O density in Ce0.97Co0.03O2-delta. The experimental results are well consistent with the F-center mediated ferromagnetism mechanism recently found in some transitional metal (TM) doped oxides, and thus is very important in understanding the mechanism of the ferromagnetism (FM) origin in many TMs-doped insulating oxides.

• 出版日期2010-6-1
• 单位电子科技大学