钇铁石榴石中铁磁共振关联的微波共振型磁介电效应调控与机理研究

The discovery of magnetodielectric effect may realize multi-modulation of microwave devices by breaking the limitation that magnetic/electric field can only tailor the permeability/permittivity in materials. However, the microwave applications of magnetodielectric effect and relative materials are hampering by some intrinsic disadvantages, such as extreme external conditions, low operating frequency and significant microwave loss etc. This proposal will focus on the physical mechanism and regulative rules of ferromagnetic resonance induced microwave resonance-type magnetodielectric effect in yttrium iron garnets which can lead to a 10 % microwave permittivity fluctuation in 2 to 8 GHz with low applied magnetic field at room temperature. The research details including: (1) excavating the internal relationship between ferromagnetic resonance and resonance-type magnetodielectric effect, analyzing the role of spinwave in the energy transportation process during the ferromagnetic resonance; (2) dissecting the extrinsic dynamic nonlinear magnetic structure with spin current theory, setting up the physical model of resonance-type magnetodielectric effect; (3) controlling the energy transportation process in inside and surface of crystal grain by modulating the spinwave spectrum, investigating the regulative rules of resonance-type magnetodielectric effect. This proposal can be expected to achieve significant progress in understanding the intrinsic physics mechanism of high frequency magnetodielectric and relieving the extant bottleneck in microwave applications of magnetodielectric effect.

磁介电效应打破了磁场（电场）只能单一调控材料磁导率（介电常数）的局限性，为微波器件的调控方式提供了额外的自由度。但极端外部条件、低作用频段以及相关材料明显的微波损耗，阻碍了磁介电效应在微波工程领域的应用。本项目以低损耗钇铁石榴石为对象，拟研究该体系中铁磁共振关联的微波共振型磁介电效应这一新现象（室温、低场条件下，2-8 GHz频段内的磁致介电常数变化率可达10%）的物理机制与调控规律。主要内容包括：（1）挖掘铁磁共振与共振型磁介电效应的内在物理联系，剖析自旋波在该过程中的能量输运作用；（2）利用自旋流理论，分析自旋波传输所导致的非固有、动态非共线磁结构，建立共振型磁介电效应的物理模型；（3）从自旋波谱调制角度出发，控制自旋波在晶粒内部与表层的能量输运过程，探究共振型磁介电效应的调控规律。研究成果将为挖掘高频磁介电效应的科学本质、突破相关材料在微波工程的现存瓶颈提供一定的理论与实验基础。

磁电耦合与磁介电效应，作为材料中磁有序与电有序间动态耦合的宏观体现，在外场调制微波器件、有源/无源微波吸收等方面有着重要应用前景。本项目以钇铁石榴石微波铁氧体作为研究目标，挖掘了铁磁共振现象与微波共振型磁介电效应的内在物理关联，基于自旋流理论建立了该效应的基础物理模型，实现了对微波磁介电效应的半定量描述；利用微磁学仿真手段，建立了基于有限元模拟方法的退磁场修正方法，获取了钇铁石榴石铁磁共振条件下的本征微波磁谱；从双磁子散射理论出发，利用Ce4+, Yb3+, Si4+等高价离子进行稀土位/铁位掺杂，以此探索、总结了微波共振型磁介电效应的调控机理，揭示了材料磁有序程度与自旋波能量输运间的竞争关系。同时，进一步定义了损耗型磁介电效应系数，以“0-3”型磁电复合材料BaTiO3-Y3Fe5O12、Ce-YIG微波铁氧体以及基于YIG微波铁氧体的超材料阵列结构中探究了微波电磁参数调谐以及有源微波吸收方面的应用，实现了良好的可调谐有源微波吸收效果。此外，还研究了一系列纳米磁电复合材料中介电常数与磁导率耦合协同效应，实现了“薄轻宽强”的无源吸波效果。本项目的研究结果为未来高频磁电耦合效应理论研究及其实际应用提供了有效的实验支持与理论指导。