Energy barrier distribution for dispersed mixed oxide magnetic nanoparticles
Energy barrier distribution for dispersed mixed oxide magnetic nanoparticles
复制标题
分散的混合氧化物磁性纳米粒子的能垒分布
DOI：
10.1063/1.3676229
复制
发表时间：
2012
影响因子：
3.2
通讯作者：
W. Schwarzacher
中科院分区：
文献类型：
--
作者：
M. Okuda;J. Eloi;A. Sarua;Sarah E. Ward Jones;W. Schwarzacher
以蛋白质铁蛋白为模板制备了直径为8 nm的Fe/Co混合氧化物纳米粒子，并通过透射电子显微镜（TEM）和拉曼光谱对其进行了表征。结果表明，后者能有效区分磁铁矿（Fe_3O_4）、磁赤铁矿（γ-Fe_2O_3）和钴铁氧体（Co_xFe_3-xO_4）。零场冷却的磁化率测量显示，孤立的磁铁矿纳米颗粒具有阻挡温度TB = 18 ± 1 K，但添加0.5%的Co将TB提高到30 K。从饱和的热弛豫数据服从T ln（t/τ0）标度，使我们能够确定分散的纳米粒子的能量势垒分布。对于Fe氧化物只有一个单峰，而当Co含量仅为0.5%时，观察到第二个组分随能量的增加而迅速减少。
Mixed Fe/Co oxide nanoparticles, diameter 8 nm, were prepared using the protein ferritin as a template and characterized by transmission electron microscopy (TEM) and Raman spectroscopy. We show that the latter effectively distinguishes between magnetite (Fe3O4), maghemite (γ-Fe2O3) and Co ferrite (CoxFe3-xO4). Zero-field-cooled susceptibility measurements show isolated magnetite nanoparticles have a blocking temperature TB = 18 ± 1 K, but that adding 0.5% Co raises TB to 30 K. Data for thermal relaxation from saturation obey a T ln(t/τ0) scaling, enabling us to determine the energy barrier distributions for the dispersed nanoparticles. For Fe oxide only a single peak was found. However, with the addition of only 0.5% Co a second component is observed that decreases rapidly with increasing energy.