基于粒径和间距独立可控的磁性纳米粒子组装复合颗粒膜的电磁输运特性研究

磁性纳米颗粒膜材料是一类非常值得重视的人工纳米功能材料，然而由于其室温磁电阻较低、饱和磁场较多层膜大，阻碍了它的广泛应用，迫切需要从制备方法、新体系开发和调制机理上开展创新性研究。本项目拟采用自行研制、具有特色的纳米粒子束流复合薄膜沉积装置，将高纯度、表面洁净、尺寸均一、粒径可调(3-20nm)的Fe、Co、Fe3O4磁性纳米粒子与非磁性相(Cr,Al2O3,MgO)进行复合，形成一种粒径和间距独立可控的磁性纳米粒子组装复合颗粒膜，力图在磁性纳米粒子的种类、尺寸均一性、尺寸大小、颗粒间距等几个自由度上实现对该新型颗粒膜体系的微结构和电磁输运特性的调控，在此基础上通过多种测试和分析手段，系统研究这些因素对GMR(TMR)效应、电阻的温度依存性、自旋相关共隧穿过程等电磁输运特性的影响规律，揭示其物理机制，探索提高颗粒膜室温和低场磁电阻的可能途径，为颗粒膜材料的开发和广泛应用提供实验和理论依据。

Magnetic nanogranular film is a noteworthy kind of artificial functional nanomaterials, however, its application was limited due to the low magnetoresistance (MR) value at room temperature and larger saturation field compared with multilayer films. Therefore, an in-depth research ranging from the development of new granular system and preparation route to modulation mechanism is of urgent need. In this project, our own designed nanoclusters beam composite film deposition system will be used. By compositing Fe, Co and Fe3O4 magnetic nanoclusters which are of high purity, clean surface and controllable uniform nanocluster size (3-20 nm) with nonmagnetic phases (Cr, Al2O3 or MgO), nanocluster-assembled composite granular films with independently controllable cluster size and intercluster spacing will be acquired. This project seeks to adjust the microstructure, electronic and magnetic transport properties of this new nanogranular film system in several degrees of freedom including types of magnetic clusters, cluster size, size distribution and intercluster spacing. On that basis, through a variety of experimental measurement and analytical tools, relationships of these factors with electronic and magnetic transport properties (GMR or TMR, temperature dependence of resistance, spin-dependent co-tunneling effect, etc.) will be studied systematically. The physical mechanism will be revealed and possible ways to enhance MR value of the granular film at room temperature at low magnetic field will be explored. This project will provide experimental and theoretical foundation for the development and wide applications of granular films.