Collaborative Research: Novel Terahertz Generators Based on Magnetic Materials

合作研究：基于磁性材料的新型太赫兹发生器

• 批准号: 1708982
• 负责人: Andrei Slavin
• 金额: $ 21.08万
• 依托单位: Oakland University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708982&HistoricalAwards=false
• 关键词: Collaborative; Research; Novel; Terahertz; Generators

Generators of electromagnetic waves with frequencies near one terahertz are needed for several types of practically useful applications such as new bio-medical imaging techniques, highly sensitive chemical sensors and energy-efficient wireless computer chips. Existing generators of terahertz radiation have significant deficiencies that severely limit their usefulness. These generators either work at temperatures below room temperature or are based on expensive and bulky laser systems. The goal of this project is to create a new type of terahertz generator that is compact, inexpensive and works at room temperature. These generators are based on readily available magnetic materials such as iron oxide and nickel oxide and will operate via conversion of magnetic oscillations in these materials into terahertz electromagnetic waves. The goal of the proposed research program will be achieved via a collaborative effort of a synergistic team of experts in magnetic device fabrication (University of California, Irvine) and leading theorists in the field of magnetic devices (Oakland University). The results of the proposed research program will impact society in multiple ways. The new method of terahertz signal generation will help maintain the US leadership in terahertz technology. A number of undergraduate and graduate students will be trained in modern device fabrication techniques, which will enhance the US nanotechnology workforce. The outreach activities, including demonstrations on magnetism and superconductivity, will target middle school students from underrepresented groups, and will help attract minorities to science and engineering.The proposed research program is based on a substantial preliminary experimental and theoretical work of the proposers, who experimentally demonstrated spin pumping in Pt/hematite bi-layers, and theoretically predicted that a bi-layer of a heavy metal (Pt) and an antiferromagnetic material with strong easy-plane and weak easy-axis magnetic anisotropies can function as a source of coherent THz radiation when direct current is applied to the Pt layer. In such antiferromagnet-based auto-oscillators, an electric current in the Pt layer injects pure spin Hall current into the antiferromagnet and drives its order parameter into a state of persistent precession. This precession excited by the component of spin current perpendicular to the easy plane anisotropy of the antiferromagnet is non-uniform in time due to the weak easy-axis magnetic anisotropy present within the easy plane anisotropy. The frequency of the antiferromagnetic order parameter oscillations is proportional to the injected spin current, and increases from approximately 0.1 THz to 2.0 THz with increasing current density in the Pt layer. The order parameter oscillations are converted into a THz electromagnetic signal with electric field amplitude exceeding 1 V/cm via spin pumping and the inverse spin-Hall effect in the Pt layer. The dynamics of the THz-frequency room-temperature antiferromagnetic auto-oscillator is mathematically equivalent to that of a Josephson junction auto-oscillator, with the energy of the weak uniaxial magnetic anisotropy of the antiferromagnet playing the role of the Josephson energy. The demonstration of these compact, tunable and structurally simple antiferromagnet-based sources of THz radiation will enable the development of compact and inexpensive solid state THz devices for imaging, chemical detection, wireless chip-to-chip communication and THz spectroscopy/microscopy.

频率接近1太赫兹的电磁波发生器需要几种类型的实际有用的应用，如新的生物医学成像技术，高灵敏度的化学传感器和节能的无线计算机芯片。现有的太赫兹辐射发生器存在严重缺陷，严重限制了其实用性。这些发生器要么在低于室温的温度下工作，要么基于昂贵而庞大的激光系统。该项目的目标是创造一种新型的太赫兹发生器，这种发生器结构紧凑，价格低廉，可在室温下工作。这些发电机基于容易获得的磁性材料，如氧化铁和氧化镍，并将通过将这些材料中的磁振荡转换为太赫兹电磁波来运行。拟议的研究计划的目标将通过一个协同工作的团队的专家在磁性设备制造（加州大学，欧文）和领先的理论家在磁性设备领域（奥克兰大学）的合作努力实现。 研究计划的结果将以多种方式影响社会。太赫兹信号产生的新方法将有助于保持美国在太赫兹技术方面的领先地位。一些本科生和研究生将接受现代设备制造技术的培训，这将提高美国纳米技术的劳动力。这些活动包括磁性和超导性的演示，将针对来自代表性不足群体的中学生，并将有助于吸引少数民族进入科学和工程领域。拟议的研究计划是基于提议者的大量初步实验和理论工作，他们通过实验证明了Pt/赤铁矿双层中的自旋泵，并且从理论上预测，当向Pt层施加直流电时，具有强易平面和弱易轴磁各向异性的重金属（Pt）和反铁磁材料的双层可以用作相干THz辐射源。在这种基于反铁磁体的自动振荡器中，Pt层中的电流将纯自旋霍尔电流注入反铁磁体，并将其序参量驱动到持续进动状态。由于易面各向异性内存在弱易轴磁各向异性，由垂直于反铁磁体的易面各向异性的自旋电流分量激发的这种进动在时间上是不均匀的。反铁磁序参数振荡的频率与注入的自旋电流成正比，并且随着Pt层中电流密度的增加而从约0.1 THz增加到2.0 THz。通过自旋泵浦和Pt层中的逆自旋霍尔效应，将序参数振荡转换为电场幅度超过1 V/cm的THz电磁信号。太赫兹频率的室温反铁磁自振子的动力学在数学上等价于约瑟夫森结自振子的动力学，其中反铁磁体的弱单轴磁各向异性的能量起约瑟夫森能量的作用。这些紧凑，可调和结构简单的反铁磁基太赫兹辐射源的演示将使紧凑和廉价的固态太赫兹设备的成像，化学检测，无线芯片到芯片通信和太赫兹光谱/显微镜的发展。

项目成果

Excitation of Whispering Gallery Magnons in a Magnetic Vortex

• DOI: 10.1103/physrevlett.122.097202
• 发表时间: 2019-03-05
• 期刊: PHYSICAL REVIEW LETTERS
• 影响因子: 8.6
• 作者: Schultheiss, K.;Verba, R.;Schultheiss, H.
• 通讯作者: Schultheiss, H.

Micromagnetic modeling of terahertz oscillations in an antiferromagnetic material driven by the spin Hall effect

• DOI: 10.1103/physrevb.99.024405
• 发表时间: 2019-01-07
• 期刊: PHYSICAL REVIEW B
• 影响因子: 3.7
• 作者: Puliafito, V;Khymyn, R.;Finocchio, G.
• 通讯作者: Finocchio, G.

Terahertz frequency spectrum analysis with a nanoscale antiferromagnetic tunnel junction

• DOI: 10.1063/1.5140552
• 发表时间: 2020-02-14
• 期刊: JOURNAL OF APPLIED PHYSICS
• 影响因子: 3.2
• 作者: Artemchuk, P. Yu.;Sulymenko, O. R.;Prokopenko, O. V.
• 通讯作者: Prokopenko, O. V.

Nonlinear spin conductance of yttrium iron garnet thin films driven by large spin-orbit torque

• DOI: 10.1103/physrevb.97.060409
• 发表时间: 2017-02
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: N. Thiéry;A. Draveny;V. Naletov;L. Vila;Jean-Philippe Attan'e;G. D. Loubens;M. Viret;N. Beaulieu;J. B. Youssef;V. Demidov;S. Demokritov;A. Slavin;V. Tiberkevich;A. Anane;P. Bortolotti;V. Cros;O. Klein

Amplification and stabilization of large-amplitude propagating spin waves by parametric pumping

• DOI: 10.1063/1.5019357
• 发表时间: 2018-01
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: R. Verba;M. Carpentieri;G. Finocchio;V. Tiberkevich;A. Slavin