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Transport phenomena in metal nanocomposites

机译:金属纳米复合材料中的传输现象

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Ferromagnetic nanocomposites are the special case of metal composites; they are of practical interest for spintronics. Temperature dependences of resistivity ρ(T) and thermoelectric power α(T) of ferromagnetic nanocomposites with the composition Co_x(Al_2O_3)_(100 - x) (36. 6 ≤ x ≤ 52. 5 at %) are investigated near the percolation threshold (x_p ≈ 43. 3 at %) in a temperature range of 77-300 K. Sizes of Co nanoparticles are no larger than 25 nm. Specific features are observed in the dependences α(T) in the form of a kink at T_b ≈ 170 K. The analysis of the structural and electrical schematics as well as energy diagrams of percolation channels of electrons shows that only the diffusion thermoelectric power appears in Co nanoparticles, at which α(T) is the linear function. No mechanisms of the thermoelectric power caused by nanosizes of Co particles or by electron tunneling between them are found. The kink of the α(T) linear dependence is explained by the existence of the oxide shell of Co nanoparticles. It is assumed that the temperature dependences of energy barriers of oxide shells of metal nanoparticles (including ferromagnetic ones) in oxygen-containing dielectric matrices determine the features of α(T) and ρ(T) dependences of such nanocomposites.
机译:铁磁性纳米复合材料是金属复合材料的特例。它们对自旋电子学具有实际意义。在渗流阈值附近研究了Co_x(Al_2O_3)_(100-x)(36. 6≤x≤52. 5 at%)组成的铁磁纳米复合材料的电阻率ρ(T)和热电功率α(T)的温度依赖性。 (x_p≈43. 3 at%)在77-300 K的温度范围内。Co纳米粒子的尺寸不大于25 nm。在T_b≈170 K处,以扭结的形式在依赖关系α(T)中观察到了特定的特征。对电子的渗流通道的结构和电气原理图以及能量图的分析表明,只有扩散热电能出现在电子中。 Co纳米粒子,其中α(T)是线性函数。没有发现由纳米尺寸的Co颗粒或它们之间的电子隧穿引起的热电机制。 Co纳米粒子的氧化物壳的存在解释了α(T)线性依赖的纽结。假定含氧介电基质中金属纳米粒子(包括铁磁粒子)的氧化物壳的能垒的温度依赖性决定了这种纳米复合材料的α(T)和ρ(T)依赖性的特征。

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