All-Optical Magnonic Spin Torque Devices

全光学磁自旋扭矩装置

• 批准号: 1231929
• 负责人: Casey Miller
• 金额: $ 36万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1231929&HistoricalAwards=false
• 关键词: Optical; Magnonic; Spin; Torque; Devices

Intellectual merit: The research objectives of this proposal are to engineer a series of spin-transfer devices whose torque originates from thermally generated magnons. It has been predicted that such heat driven spin torque can lead to quantum yield improvements nearly two orders of magnitude greater than present state-of-the-art current-drive spin torque devices. Increasing the usable spin torque with all else constant will have a major impact on spin torque device technologies. Given the great potential, magnonic spin torque devices will be fabricated using a combination of thin film deposition and nanolithography techniques. Device structures will include magnetic oxide-normal metal-metallic ferromagnet spin valves. The operation and characterization of device performance will be entirely optical: ultrafast pump-probe time-resolved Magneto-Optical Kerr Effect to first excite magnons in the oxide, then observe the resulting magnetization dynamics in the metallic ferromagnet. The underlying principle of these devices is the transfer of spin momentum from magnons in a magnetic oxide to the magnetization of a free ferromagnetic layer. Magnons will be generated in the magnetic oxide layer (e.g., a spinel ferromagnet) by an femtosecond laser pulse. These magnons will annihilate at the oxide-normal metal interface (which may contain an additional layer of magnetic atoms), but their spin momentum will be transferred to conduction electrons in the normal metal. Thus, a time dependent accumulation of spin polarized electrons will be generated in the normal metal. The time derivative of this spin accumulation results in a torque on the metallic ferromagnet, which emphasizes the importance of using ultrafast optics. Device performance will be optimized through materials selection, creating and characterizing interfaces amenable to spin transfer, and investigating relevant length scales.Broader Impacts: The experimental realization of magnonic spin torque devices whose quantum yield is improved by nearly two orders of magnitude beyond the present state-of-the-art will have transformative impact by essentially creating a new class of spin torque devices. Spin-transfer torque devices in general would benefit from replacing the high current densities now necessary for operation, as this causes appreciable heating, and vortex nucleation in the free layer via the unavoidable Oersted field. Magnonic spin torque would address these issues, allowing significant improvements in device performance, fabrication requirements, and reliability. This program will integrate teaching and training of students by unifying techniques and ideas from physics, electrical engineering, and materials and optical sciences, thereby empowering them with the multidisciplinary talents necessary to become the next generation of leaders in academia and industry. An international collaboration will underscore the importance of global collaborations for modern research. The PIs will continue to build upon their established records of broadening the participation of underrepresented groups through a variety of means, including: mentoring students from USF?s Florida-Georgia Louis Stokes Alliance for Minority Participation Bridge to the Doctorate Program; educating the community about the disproportionate filtering of underrepresented groups by certain admissions policies; organizing summer camps for minority-serving middle schools in collaboration with the Florida Advanced Technological Education Center (FLATE), a NSF-ATE Regional Technological Education Center of Excellence. In collaboration with FLATE and the Hillsborough County School District, additional effort will help develop a science, technology, engineering, and math proficient workforce through training workshops for teachers.

智力优点：该提案的研究目标是设计一系列旋转转移设备，其扭矩起源于热产生的镁。据预测，这种热驱动的自旋扭矩会导致量子收率提高近两个数量级，比当前最新的电流驱动旋转扭矩设备大两个数量级。增加可用的自旋扭矩和其他所有常数将对自旋扭矩设备技术产生重大影响。鉴于巨大的潜力，将使用薄膜沉积和纳米光刻技术的组合来制造宏伟的旋转扭矩设备。设备结构将包括磁氧化物正常金属金属铁磁旋转阀。设备性能的操作和表征将完全是光学的：超快速泵探针时间分辨的磁磁光kerr效应首先激发氧化物中的镁，然后观察金属铁磁铁中所得的磁化动力学。这些设备的基本原理是自旋动量从磁氧化物中的木元素转移到游离铁磁层的磁化。镁将通过飞秒激光脉冲在磁氧化物层（例如尖晶石铁磁铁）中产生。这些镁将在氧化物正常的金属界面上消灭（可能包含额外的磁原子），但它们的自旋动量将转移到正常金属中的传导电子。因此，在正常金属中将产生自旋极化电子的时间依赖性积累。这种自旋积累的时间导数导致金属铁磁铁上的扭矩，该扭矩强调了使用Ultrafast光学元件的重要性。设备性能将通过选择材料，创建和表征可旋转转移的界面，并研究相关的长度尺度。Boader的影响：宏伟的旋转扭矩设备的实验实现，其量子产量通过近两个数量级的量子提高了当前最新的量子，而当前最新的ART将通过基本上产生新的Spin Spin旋转器设备的变化影响。通常，自旋转移扭矩设备将受益于更换现在操作所需的高电流密度，因为这会导致可观的加热，并且通过不可避免的Oerstered场中的自由层中的涡旋成核。 Magnonic自旋扭矩将解决这些问题，从而可以显着改善设备性能，制造要求和可靠性。该计划将通过统一物理，电气工程以及材料和光学科学的技术和想法来整合学生的教学和培训，从而使他们赋予他们成为学术界和行业领导者的下一代领导者所必需的多学科才能。国际合作将强调全球合作对现代研究的重要性。 PI将继续基于他们既定的记录，即通过各种手段来扩大代表性不足的团体的参与，包括：从USF的佛罗里达州佛罗里达州 - 乔治亚 - 乔治亚 - 乔治亚 - 乔治亚·斯托克斯·斯托克斯联盟（Louis-Georgia-Georgia-Georgia-Georgia Stokes Alliance of Bigartion Bridge）登上博士学位课程；通过某些招生政策对社区进行不成比例的过滤群体的过滤；与佛罗里达州高级技术教育中心（FLATE）合作，为少数族裔服务中学组织夏令营，这是NSF-ate地区技术教育卓越中心。通过与Flate和Hillsborough县学区合作，额外的努力将通过为教师的培训讲习班来开发科学，技术，工程和数学熟练的劳动力。