采用水热法制备了Co掺杂的SnO_2纳米棒.随着Co掺杂浓度的增加,样品的室温铁磁性先增加后降低,当Co掺杂浓度为4%时,样品的饱和磁化强度达到最大值.纳米棒呈花簇状生长,单根纳米棒长度约300 nm,为单晶金红石型SnO_2相.X射线光电子能谱和X射线近边结构谱分析表明,Co在SnO_2样品中以+2价态存在,替代了Sn~(4+)离子的位置,并未与其它元素形成杂质相,从而证明室温铁磁性为Sn_(1-x)Co_xO_2纳米棒的本征性能.同时,采用自旋分裂杂质带模型,解释了Co掺杂浓度对样品室温铁磁性的调节作用.
SnO_2 nanorods with different concentration of Co dopants were prepared by hydrothermal method. With the increase in the concentration of Co, room temperature ferromagnetism of the samples initially increases and then decreases. The highest value of saturated magnetization occurs in the sample with the Co concentration of 4%. Morphology analyses indicate that the nanorods grow in flower cluster, and the length of single nanorod is approximate 300 nm. XPS and XANES techniques reveal a solid solution of Co dopants in SnO_2 lattice, where Co is in 2+ oxidation state substituting for Sn~(4+). Due to the elimination of impurity phases, it is confirmed that the observed ferromagnetism is the intrinsic nature of the system. Using impurity band model, we demonstrate the dependence of ferromagnetism on Co concentration and elucidate the origin of ferromagnetism.
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