基于铁氧体铁磁共振的超材料设计与电磁特性研究

Metamaterials, especially left-handed materials and cloaking system, have attracted great attentions in the fields of physics and materials due to their exotic electromagnetic properties. Most metamaterials designs have so far been based on metallic structures, such as split rings. Those metamaterials are faced with the increasingly difficulties in processing, losses and tunability. In this project, we focus on the design and extraordinary electromagnetic behaviors of metamaterials based on ferromagnetic resonance. The negative permeability of the ferrite can be obtained when the ferromagnetic resonance takes place. By using the intrinsic properties of ferrites, the metamaterials with extraordinary electromagnetic behaviors can be obtained, which could overcome the above-mentioned difficulties. The effect of magnetic parameters such as saturation magnetization, magnetocrystalline anisotropy field and demagnetization field on the electromagnetic properties of metamaterials will be studied. Through the structure optimization design of metamaterials, the extraordinary electromagnetic properties with high frequency, broadband or multi-band will be realized. The physical mechanisms and preparation methods for ferrite-based metamaterials will be explored, and the permanent magnetic ferrite-based metamaterial which can exhibit negative refraction without applied magnetic field will also be prepared. The ferrite-based metamaterials with thermo-tunable negative refractive index can be obtained because the magnetic properties of the ferrite show a transition from ferrimagnetic to paramagnetic near the Curie temperature. This project offers new directions for the design of electromagnetic metamaterial devices.

以“左手材料”和“超隐身系统”为代表的超材料由于具有奇特的电磁传输特性而成为当今物理和材料领域的研究热点。目前，研究者大多采用人工金属结构类超材料来实现左手特性或负折射性能。此类超材料的发展已经受到加工难、损耗高以及可调性差等因素的严重影响。本项目拟研究一种基于铁氧体铁磁共振的超材料及其超常电磁特性。通过铁氧体的铁磁共振实现本征负磁导率进而制备出具有超常电磁特性的本征型超材料，突破超材料发展的若干瓶颈问题；探讨饱和磁化强度、磁晶各向异性场以及形状退磁场等磁性能参数对超材料电磁性能的影响规律，建立各参数与可调电磁特性的关系，进而通过对铁氧体基超材料的结构优化设计，实现高频、宽频或多频性能；研究实现本征型铁氧体基超材料的物理机制与方法，制备出无需外场的永磁铁氧体基超材料；利用铁氧体磁化强度在其居里温度附近显著变化这一特点，设计出温控负折射超材料，为电磁超材料器件的设计开辟新的方向。

电磁超材料由于具有奇特的电磁传输特性而成为当今物理和材料领域的研究热点。目前，研究者大多采用人工金属结构类超材料来实现左手特性或负折射性能。此类超材料的发展已经受到加工难、损耗高以及可调性差等因素的严重影响。. 本项目设计出了多种基于铁氧体铁磁共振的超材料及超材料微波器件，并研究了其超常电磁特性。理论研究方面，我们通过铁氧体的铁磁共振实现本征负磁导率；探讨了饱和磁化强度、磁晶各向异性场以及形状退磁场等磁性能参数对超材料电磁性能的影响规律，建立了各参数与可调电磁特性的关系。在超材料设计方面，我们利用铁氧体铁磁共振与介电颗粒米氏谐振的耦合作用设计出了多种磁场调节介电常数的介质超材料，介电常数可增大400%。在超材料器件设计方面，我们利用铁氧体超材料结构设计出了磁可调宽带微波带阻和带通滤波器，结果显示：带阻滤波器的-3dB带宽为500MHz、峰值吸收-47dB、插入损耗-1dB，带通滤波器的-3dB带宽为700MHz、带外抑制-30dB、插入损耗-2.2dB；利用铁氧体和金属板复合结构设计出了磁可调宽带带通滤波器，结果显示：随着磁场从3000Oe增大到3400Oe，该滤波器的中心频率从9.8GHz调节至11.2GHz，-10dB带宽从0.8GHz增大至1.3GHz。. 本项目从铁磁共振理论出发，设计出了多种具有可调特性的超材料，解决了传统超材料可调性差的问题。此外，本项目还制备出了多种结构简单、损耗低的超材料微波器件，不仅推动了超材料的实际应用，而且为微波器件的设计提供了更多的可能。