Vacancy-Induced Ferromagnetism in SnO 2 Nanocrystals: A Positron Annihilation Study
Vacancy-Induced Ferromagnetism in SnO 2 Nanocrystals: A Positron Annihilation Study
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DOI：
10.1088/0256-307x/30/2/027804
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发表时间：
2013-02
影响因子：
3.5
通讯作者：
Zhiyuan Chen;Zhiqiang Chen;R. Pan;Shao-jie Wang
中科院分区：
文献类型：
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作者：
Zhiyuan Chen;Zhiqiang Chen;R. Pan;Shao-jie Wang
将SnO2纳米粉末压制成颗粒并在空气中从100 ° C至1400°C退火。XRD和拉曼光谱都证实了所有退火样品都是具有四方金红石结构的单相。退火诱导的SnO2晶粒尺寸从30纳米到83纳米的增加。正电子湮没测量结果显示晶界区存在空位缺陷，在400°C以下退火后，界面缺陷保持稳定，然后随着退火温度的升高逐渐恢复到1200°C。在1200°C以下退火的SnO2纳米晶具有室温铁磁性，并且随着退火温度的升高，其磁化强度不断降低。然而，铁磁性在1200°C退火时消失。这与纳米晶体中界面缺陷的恢复具有很好的一致性，表明铁磁性可能是由界面区域的空位缺陷引起的。
SnO2 nanopowders were pressed into pellets and annealed in air from 100 to 1400°C. Both XRD and Raman spectroscopy confirm that all annealed samples were single phase with a tetragonal rutile structure. Annealing induces an increase in the SnO2 grain size from 30 to 83 nm. Positron annihilation measurements reveal vacancy defects in the grain boundary region, and the interfacial defects remain stable after annealing below 400°C, then they are gradually recovered with increasing annealing temperature up to 1200°C. Room temperature ferromagnetism was observed for SnO2 nanocrystals annealed below 1200°C, and the magnetization decreases continuously with increasing annealing temperature. However, the ferromagnetism disappears at 1200°C annealing. This shows good coincidence with the recovery of interfacial defects in the nanocrystals, suggesting that the ferromagnetism is probably induced by vacancy defects in the interface region.