Electrical properties of nanocrystalline magnetite with large non-stoichiometry, near Verwey transition
Electrical properties of nanocrystalline magnetite with large non-stoichiometry, near Verwey transition
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近 Verwey 转变的大非化学计量纳米晶磁铁矿的电学性质
DOI：
10.1016/j.jmmm.2008.10.011
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发表时间：
2009
影响因子：
2.7
通讯作者：
D. Chakravorty
中科院分区：
文献类型：
--
作者：
P. Brahma;S. Dutta;D. Dutta;Souri Banerjee;A. Ghosh;D. Chakravorty
在10-300K的温度范围内，对平均粒径为50nm的磁铁矿压实粉末进行直流电测量。通过穆斯堡尔光谱分析估计了非化学计量学。在93-300K温度范围内的高分辨率x射线衍射研究未显示任何相变。80K左右电阻率变化剧烈，但无间断现象。在Mott的小极化子模型和变范围跳变模型的基础上，分别分析了电阻率与温度的关系。从这一分析中估计的韦氏温度为93K。从电压-电流特性可以看出，在跃迁温度以上费米能级存在一个小的本征间隙，而在跃迁温度以下，本征间隙急剧增大。这是由于随着温度的降低，从短程秩序向远程秩序的转变。
DC electrical measurements were carried out on compacted powders of magnetite with an average particle diameter of 50nm over the temperature range 10–300K. The non-stoichiometry was estimated from Mossbauer spectroscopy analysis. High-resolution X-ray diffraction studies in the temperature range 93–300K did not show any phase transition. There was a drastic change in resistivity around 80K but no discontinuity thereof. Electrical resistivity vs. temperature data were analysed on the basis of Mott's small polaron and variable-range hopping models, respectively. The Verwey temperature as estimated from this analysis was 93K. From voltage–current characteristics it was concluded that there was a small intrinsic gap at the Fermi level above the transition temperature and the same increased drastically below the transition temperature. This was ascribed to a transition from short-range order to long-range order as the temperature was lowered.