非稀土MnxZ（Z=Ga,Al,Bi)纳米复合永磁薄膜材料的磁硬化与磁交换耦合机制研究

The non-rare earth nanocomposite permanent magnetic films consisting of magnetic hard phase Mn-Ga, Mn-Al, Mn-Bi and magnetic soft phase Fe or FeCo will be prepared by magnetron sputtering technique, at different buffer layers, substrate layers and substrate temperatures. Influences of magnetocrystalline anisotropy of hard phase layer and the ratio of hard and soft phase layer on magnetic properties，exchange coupling and the coercivity mechanism will be investigated. The relationship of magnetic properties, exchange coupling and phase component, distribution, volume ratios, phase structure, grain orientation and size etc. will be studied systemically in nanocomposite films. The morphology and microstrcture of surface and interface of the multilayer films will be characterized by means of plane and cross-section TEM observation. Influences of applied temperature and field on distribution of the magnetic domains of the interface and interlayer of the samples will be investigated by using MFM equipped in PPMS. The relationship and regularity between magnetic properties, magnetic exchange coupling and structure, defect and magnetic structure of the films will be found out. The effect of the orientation degree of the hard phase on exchange coupling between nanograins will be investigated by mean of remanence analysis and Kromüller technique. Combined with the micromagnetic simulation, the coercity mechanism and characteristic of exchange coupling between hard and soft phases in nanocomposite permanent magnetic films will be given, and the micromagnetic theory on nanocomposite permanent magnetic films will be improved, which will offer a role of guard for the development of nanocomposite permanent magnets.

采用磁控溅射方法制备由Mn-Ga、Mn-Al和Mn-Bi硬磁相和Fe或FeCo软磁相组成的非稀土纳米复合永磁薄膜。研究硬磁相的各向异性和软磁和硬磁的比例对磁性、交换耦合机制和矫顽力机制的影响。系统研究纳米复合薄膜磁体中硬磁相和软磁相的相组成、分布、体积分数、相结构、晶粒取向和尺寸等结构因素与纳米晶粒间交换耦合和磁性的关系。研究不同的隔离层材料和厚度对硬磁相的取向和有效的交换耦合长度的影响规律。表征薄膜材料的界面及表面的结构和形貌特征，研究外加温度和磁场对薄膜磁畴分布的影响，分析归纳微结构、缺陷、磁畴分布等因素对交换耦合机制和磁性的影响，找出其内在的规律。使用剩磁分析技术并结合微磁学模拟方法，研究磁交互作用与薄膜结构和磁结构的关系以及硬磁相取向程度对纳米晶粒间交换耦合的影响；阐明非稀土纳米复合薄膜磁体硬磁相和软磁相间交换耦合特点和矫顽力机制，对进一步发展纳米复合永磁体提供有效的指导作用。

采用磁控溅射方法制备由Mn-Ga、Mn-Al和Mn-Bi硬磁相和Fe或FeCo软磁相组成的非稀土纳米复合永磁薄膜。同时采用采用熔炼及快淬工艺制备了一系列Mn基合金。研究了硬磁相的各向异性和软磁和硬磁相的比例对磁性、交换耦合和矫顽力机制的影响。系统研究了纳米复合薄膜磁体中硬磁相和软磁相的相组成、分布、体积分数、相结构、晶粒取向和尺寸等结构因素与纳米晶粒间交换耦合和磁性的关系。研究了不同的隔离层材料和厚度对硬磁相的取向和有效的交换耦合作用的影响规律。通过调节基片温度和薄膜厚度得到了不同磁性的薄膜，并得到了矫顽力达9 kOe 的MnGa薄膜，而高矫顽力源于在Si/SiO2基片上生长的MnGa薄膜具有孤立岛状生长特性，并通过磁性研究得出MnGa薄膜和薄带的矫顽力机制为形核控制型。总结出软磁层厚度对MnBi薄膜中软磁相与硬磁相之间的交换耦合作用的影响。MnBi/Fe纳米复合薄膜表现出剩磁增强效应，300 K时的最大磁能积从7.6 MGOe提高到8.0 MGOe，400 K时从5.7 MGOe提高到6.0 MGOe。类似于MnBi合金正的矫顽力-温度关系，D022-Mn3(Ga,Sn)薄带的磁晶各向异性随温度升高而增大，从而导致样品的矫顽力增加，显示出正温度系数现象。发现MnAl合金薄带在场冷低温条件下存在强烈的交换耦合作用。在MnPdGa体系中首次观察到了的室温、高密度、低磁场驱动的双斯格明子，为斯格明子器件应用提供了良好的基础。揭示出Ni2In-type MnCuGa合金中存在的团簇自旋玻璃态现象。根据以上总结，我们的研究结果为纳米复合永磁薄膜材料制备工艺提供了指导，从而达到提高这种新材料技术磁性的目的。本项目的研究也为拓展Mn基合金在磁记录、自旋电子学器件、永磁应用领域提供了依据。