Ferromagnetism as a universal feature of nanoparticles of the otherwise nonmagnetic oxides
Ferromagnetism as a universal feature of nanoparticles of the otherwise nonmagnetic oxides
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DOI：
10.1103/physrevb.74.161306
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发表时间：
2006-10-01
影响因子：
3.7
通讯作者：
Rao, C. N. R.
中科院分区：
文献类型：
--
作者：
Sundaresan, A.;Bhargavi, R.;Rao, C. N. R.
在非磁性氧化物如CeO2， Al2O3, ZnO， In2O3和SnO2的纳米颗粒（7-30 nm直径）中已经观察到室温铁磁性。CeO2和Al2O3纳米颗粒的饱和磁矩与掺杂过渡金属的宽带半导体氧化物的饱和磁矩相当。其他氧化物纳米颗粒表现出稍低的磁化值，但具有明显的滞后行为。相反，通过在空气或氧气中高温烧结纳米颗粒获得的大块样品变得抗磁性。由于没有磁性杂质存在，我们假设铁磁性的起源可能是纳米颗粒表面氧空位引起的局域电子自旋矩之间的交换相互作用。我们认为铁磁性可能是金属氧化物纳米颗粒的普遍特性。
Room-temperature ferromagnetism has been observed in nanoparticles (7-30 nm diam) of nonmagnetic oxides such as CeO2, Al2O3, ZnO, In2O3, and SnO2. The saturated magnetic moments in CeO2 and Al2O3 nanoparticles are comparable to those observed in transition-metal-doped wideband semiconducting oxides. The other oxide nanoparticles show somewhat lower values of magnetization but with a clear hysteretic behavior. Conversely, the bulk samples obtained by sintering the nanoparticles at high temperatures in air or oxygen became diamagnetic. As there were no magnetic impurities present, we assume that the origin of ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of nanoparticles. We suggest that ferromagnetism may be a universal characteristic of nanoparticles of metal oxides.