磁铁矿颗粒指前频率因子的精确测定

项目名称： 磁铁矿颗粒指前频率因子的精确测定

项目编号： No.41204053

项目类型： 青年科学基金项目

立项/批准年度： 2013

项目学科： 地球物理学和空间物理学

项目作者： 曹长乾

作者单位： 中国科学院地质与地球物理研究所

项目金额： 25万元

中文摘要： 指前频率因子是磁性颗粒固有的自旋弛豫频率，它是尼尔理论的一个基本磁学参数，对于磁性颗粒的弛豫时间的确定至关重要。但是由于极难获得无磁相互作用、粒径均一、形状相似的磁铁矿样品，难以通过实验测定指前频率因子值。人源磁性铁蛋白是通过生物矿化仿生合成的具有磁铁矿内核和铁蛋白外壳的核-壳型复合体,具有无磁相互作用、粒径均一、形状相似和矿物相单一的独特优势。本项目拟以人源磁性铁蛋白为研究对象，利用低温交流磁化率、热剩磁弛豫过程、低温穆斯堡尔谱测量等多种手段分析，结合磁学理论模拟，精确测定磁铁矿的指前频率因子值。此外，把磁性铁蛋白作为超顺磁磁铁矿颗粒模型，研究粒径和含量变化对其磁学参数的影响。

中文关键词： 超顺磁磁铁矿；指前频率因子；磁性铁蛋白；磁共振成像；

英文摘要： The pre-exponential frequency factor is the intrinsic spin frequency of magnetic particle, which is a very important basic parameter in Né theory for determining the values of relaxation times. However, its value is still not accurately determined, due to no appropriate sample with no interaction, narrow size distribution and uniform shape for magnetic characterization. Ferrimagnetic human ferritin is a novel magnetite material synthesized in a biomimetic way. The cage-like structure renders each magnetite core encapsulated by a protein shell, which makes magnetite nanoparticles non-interacting, narrow-size distributed, shape uniform and ramdomly oriented. Due to its special properties, it serves as a perfect model for understanding basic magnetic properties of magnetite particles. The purpose of this project is to determine accurately the value of pre-exponential frequency factor through studying the ferrimagnetic human ferritin combining with different magnetic measurement techniques such as alternating current susceptibility, thermal relaxation under low temperature and M?ssbauer spectroscopy measurements. Furthermore, we use ferrimagnetic human ferritin as a model to investigate the effect of size distribution and quantity on magnetic properties of superparamagnetic magnetite particles.

英文关键词： Superparamagnetic magnetite；pre-exponential frequency factor；ferrimagnetic human ferritin；magnetic resonance imaging；