高能效可重构磁振子晶体功能器件的基础研究

Magnonic crystals (MCs), which are artificial magnetic periodic structures with feature size of the order of the magnon wavelength, have tailored band structure for spin waves. The wavelength of spin wave in MCs is orders of magnitude shorter than that of electromagnetic wave of photonic crystals at the same frequency. Therefore magnetic nanodevices based on MCs are promising candidates for the integration of magnetic functional devices for design of novel features in the electromagnetic properties in the GHz-THz frequency range. The proposal puts forward an original energy-efficient electrical-modulating reconfigurable MCs which are realized by combining the spin-torque induced magnetization reversal produced by spin-hall effects (SHE) with voltage-controlled magnetic anisotropy (VCMA) in magnetic microstructures. The proposal will study deeply on mechanisms of magnetic damping, giant SHE and VCMA. The main goals of the proposal are grasping the methods to enhance the effective spin hall angle in order to decrease the critical spin-polarized current density, which is produced by SHE to induce local magnetization reversal in magnet, understanding the coupling of magnetic microstructure on spin-polarized current and electric field, establishing the relation of spin wave dispersion of reconfigurable MCs modulated by electric methods. All these works in the proposal will lay the foundation to design and fabricate magnetic functional devices based on energy-efficient reconfigurable MCs.

磁振子晶体是指具有自旋波带隙特性的人工周期性磁结构。由于在同样频率下，自旋波的波长比电磁波的波长更短，利用磁振子晶体更易实现磁功能器件的集成化，满足片上微波信号处理与通信应用的需要。项目提出将自旋霍尔效应产生的自旋转矩效应与电压控制磁各向异性两种手段结合来实现磁性体中局域性能的改变，构建高能效的电调可重构磁振子晶体器件。项目将通过磁阻尼机制与巨自旋霍尔效应机理的深入研究，掌握增大铁磁薄膜的有效自旋霍尔角的方法，达到降低自旋霍尔转移矩的临界电流密度的目的。进一步通过电场控制磁各向异性机制的研究，以及电场调制自旋霍尔转矩翻转的栅电极结构优化设计，掌握微磁结构与自旋电流和电场之间的耦合机理，建立电调磁振子晶体的自旋波色散关系，为设计与构建电可调高能效可重构功能磁振子晶体器件奠定基础。

目前微电子器件继续按照“摩尔”发展受到了严重的漏电流和热耗散问题的制约，研究后摩尔时代的替代技术尤为迫切。磁振子自旋电子学通过研究磁系统中自旋波的激发、传输、操纵与检测，探索采用自旋波作为信息载体开展信息处理和逻辑计算的可能途径，因自旋波具有低能耗和波计算能力等特点，因而广受关注。.本项目围绕高能效可重构磁振子晶体与器件的要求，从材料制备与器件设计两方面重手进行相关研究。研究利用直流磁控溅射方法制备CoFeB薄膜，采用液相外延技术在单晶石榴石基片沉积单晶钇铁石榴石（YIG）薄膜；采用界面应变缓冲层、扩散阻挡层、形核种子层等调控YIG薄膜晶体结构与磁各向异性。构建新型“重金属/YIG”自旋异质结构，优化制备工艺，提高样品生长质量。采用铁磁共振和逆自旋霍尔效应表征CoFeB、YIG单晶薄膜共振线宽及吉尔伯特损耗，深入研究了两种磁性薄膜磁阻尼机制与磁性异质结的自旋霍尔效应增强机理。基于微磁学模拟设计可重构自旋波磁振子晶体、自旋波波导和自旋波定向耦合器等功能器件。.本项目研制出了材料阻尼因子控制在～10-4量级水平的YIG基系列薄膜，找到了低损耗自旋波媒质材料的精控生长方法，以及与半导体异质集成的技术，提出多种基于自旋-轨道矩的电流和电调磁各向异性控制的可重构纳米自旋波功能器件。这些研究为自旋波异质结器件的开发打下了坚实的基础。.在项目执行期间，发表论文28篇，其中SCI论文27篇；申请中国发明专利10项，其中授权3项；在读博士研究生2名，毕业硕士研究生4名。

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