Nd-Fe-B/α-Fe基纳米复合多层膜的界面析出及其交换耦合的研究

The interfacial microstructures between soft and hard magnetic phases decide the magnetic properties of nanocomposite magnets through affecting the exchange coupling. In this project, the Nd-Fe-B (hard magnetic phase)/α-Fe (soft magnetic phase) based nanocomposite magnetic film will be investigated. Because of the existence of lots of voids and dislocation microstructural defects, the interfaces between hard magnetic and soft magnetic phases could become the nucleation sites of the precipitates. These interfacial structural features will be made good use of. The super-saturated Fe-based solid solutions with the solutes (Nd, Cu, Nb or Si) will be prepared by magnetron sputtering through changing the target compositions. The supersaturated solutes or their compounds will precipitate at the interfaces during the heat treatment of sputtered thin films to modify the interfacial microstructures. The detailed evolution of the interfacial structures, atomic diffusion of supersaturated solutes will be carefully characterized by using electron transimission microscopy (TEM), electron energy loss spectroscopy (EELs). The exchange coupling and its change with interfacial microstructures will be clarified using magnetic measurements. A intrinsic relationhsip between exchange coupling and interfacial microstructures will be obtained. An optimum technique of interfacial precipitation will be achieved to improve the magnetic properties of nanocomposite multilayered magnetic films and its physical mechanism will be revealed.

软磁相与硬磁相之间的界面微结构影响两相之间的交换耦合，从而决定纳米复合磁体的磁性能。本项目以Nd-Fe-B（硬磁相）/α-Fe（软磁相）基纳米复合磁性多层膜为研究对象，利用硬磁相/软磁相层界面含大量原子空位、位错等结构缺陷易成为析出相形核核心的优势，首先调控α-Fe软磁层溅射靶材成份，溅射含Nd、Cu、Nb或Si的Fe（Nd）、Fe（Cu）、Fe（Nb）及Fe（Si）过饱和固溶体软磁层，再优化溅射后续退火处理工艺，促使过饱和固溶体软磁层中过饱和元素或其化合物在界面析出，从而修饰和调控磁性层之间的界面微观结构。使用透射电子显微镜、电子能量损失谱等技术表征复合薄膜磁性层界面的微结构演变过程，归纳不同过饱和元素或其化合物在界面处的析出规律。通过磁性测量分析软磁层和硬磁层之间的交换耦合行为及交换耦合作用随界面微结构演变的规律，获得提高纳米复合磁性多层膜磁性能的最佳界面析出工艺，归纳其物理机理。

软磁相与硬磁相之间的界面微结构影响两相之间的交换耦合，从而决定复合磁体的磁性能。本项目系统调控Nd-Fe-B /α--Fe 基多层膜的结构，优化了溅射后的退火工艺，成功制备了矫顽力为26.5 kOe的复合多层膜磁体，构建了薄膜磁体结构-退火工艺-磁性能之间的关系。主要研究进展如下：.(1)选择富钕Nd-Fe靶及富铁Nd-Fe-B靶优化复合薄膜的微观结构，观察到Si/Ta/[Nd-Fe (富Nd)/Nd-Fe-B (富Fe)]10/Ta多层膜结构有利于提高矫顽力，退火处理后获得的最大矫顽力约21 kOe，并且薄膜呈现为垂直磁各向异性。详细的结构表征揭示了调控薄膜结构和退火工艺使薄膜磁体矫顽力提高的机理。.(2) 为了揭示退火过程中元素的迁移及成相行为，分析薄膜微观结构-磁性能的本征关系，采用TEM和XPS技术对薄膜样品退火过程中Ta、Fe、B、Nd等原子分布及其成相过程进行了细致研究，进一步阐明了退火工艺对薄膜磁体磁性能的影响机制。.(3)为进一步提高磁性能，参照典型烧结磁体Nd15Fe77B8成分并且引入PrCu层，设计并制备了Ta(20 nm)/PrCu(2, 4, 6, 8, 10 nm)/Nd-Fe(36 nm)/Nd-Fe-B(41 nm)/PrCu(2, 4, 6, 8, 10 nm)/Ta(20 nm)薄膜。结果表明，较之于未引入PrCu层的薄膜磁体，含有PrCu层的薄膜磁体的矫顽力、剩磁及饱和磁化强度均明显提高。当Ta(20 nm)/PrCu(4 nm)/Nd-Fe(36 nm)/Nd-Fe-B(41 nm)/PrCu(4 nm)/Ta(20 nm)的矫顽力提高至 26.5 kOe。.(4)拓展研究了Dy2O3掺杂对Nd2Fe14B/α-Fe纳米复合磁体磁性能的影响。结果表明, 掺入 Dy2O3能显著提高复合磁体的矫顽力, 且随着 Dy2O3掺杂量的增大最大矫顽力对应的退火温度降低。揭示了复合磁体矫顽力的增强主要归因于硬磁相磁晶各向异性的提高。.(5)发表了学术研究论文9篇（其中SCI收录6篇，EI收录3篇），另有2篇论文已投稿。参加国际国内学术会议5人次，培养硕士研究生7人。