The influence of temperature on the magnetic behavior of colloidal cobalt nanoparticles
The influence of temperature on the magnetic behavior of colloidal cobalt nanoparticles
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DOI：
10.1109/tmag.2007.893865
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发表时间：
2007-06-01
影响因子：
2.1
通讯作者：
Shull, R. D.
中科院分区：
文献类型：
--
作者：
Dennis, C. L.;Cheng, G.;Shull, R. D.
磁性纳米颗粒的应用，包括用于癌症治疗的热疗，需要了解胶体环境如何影响纳米颗粒的磁性。本文采用在1,2-二氯苯（DCB）中热分解合成的10 mn直径的钴纳米颗粒，研究了胶体环境对这种材料磁性行为的影响。在零场冷却条件下，通过磁化强度(M)与温度(T)的测量和矢量磁强计对样品的磁性进行了研究。在M与T数据中特别有趣的是，在样品加热期间，在DCB熔点周围观察到磁化强度的连续上升，而在样品冷却期间，在DCB过冷点周围观察到磁化强度的不连续下降。矢量磁强计测量量化样品对施加磁场无响应的部分。当温度通过DCB中的过冷点冷却时，这种未反转分量的大小随着温度的降低而翻倍。随着液固转变的进行，样品的单轴各向异性也从61.1(7)X 10(-7) J增加到104.2(9)X 10(-7) J。
Applications of magnetic nanoparticles, including hyperthermia for cancer treatments, require knowledge of how the colloidal environment affects the magnetic properties of the nanoparticles.. Here, 10 mn diameter cobalt nanoparticles synthesized by thermodecomposition in 1,2-dichlorobenzene (DCB) are used to study the effect of the colloidal environment on the magnetic behavior of such materials. The magnetic properties are investigated by magnetization (M) versus temperature (T) measurements and vector magnetometry performed on the samples under zero-field-cooled conditions. Of particular interest in the M versus T data is a continuous rise in the magnetization observed around the DCB melting point during sample heating and a discontinuous drop around the DCB supercooling point during sample cooling. Vector magnetometer measurements quantify the portion of the sample that does not respond to the applied field. The magnitude of this unreversed component doubles with decreasing temperature as the temperature cools through the supercooling point in DCB. There is also an increase in the uniaxial anisotropy of the sample from 61.1(7) X 10(-7) J to 104.2(9) X 10(-7) J as the liquid-to-solid transition is traversed.