SHF: Small: Collaborative Research: Skyrmion Mediated Energy-efficient VCMA Switching of 2-Terminal p-MTJ Memory

最先进的磁存储设备使用电流将纳米磁铁的磁化强度从“上”切换到“下”状态，反之亦然，从而分别编码二进制位1和0。与基于广泛使用的CMOS（互补金属氧化物半导体）技术的器件不同，这种基于自旋传递扭矩随机存取存储器（STT-RAM）技术的器件是非易失性的，这是一个显著的优势。然而，这些器件消耗的能量大约是CMOS器件用于开关的1000倍。如果用电场来控制磁化强度，这些装置的能源效率将提高一百倍。然而，由于材料缺陷和材料中的室温热噪声的存在而引入的误差水平阻碍了这种控制方法的发展。该项目旨在展示新技术，使开关和控制过程对此类缺陷具有鲁棒性，从而实现该技术与CMOS器件竞争所需的节能。该项目还将帮助指导本科生暑期研究，各种K-12纳米磁性计算研讨会。该项目旨在证明，通过所谓的中间“磁性斯基米子状态”来强制磁化，在这种状态下，磁化从核心向上/向下螺旋指向圆形纳米磁铁的外围向下/向上，这使得开关过程非常稳健，并且消除了对任何额外磁场的需要。这种器件的开发，如果成功的话，可以使节能的磁各向异性电压控制（VCMA）开关技术在实际存储器件中可行，而只需要对现有的STT-RAM制造工艺进行适度的改变。本研究项目的关键技术方法将解决知识上的空白，并展示skyrmion介导的纳米磁存储器件的概念验证。该项目计划1)研究各种材料系统和界面的增长，并表征其磁性，以开发一种节能、可扩展且开关误差低的优化存储器件；2)演示由skyrmion状态介导的纳米磁性存储单元的VCMA开关的概念验证，并表征其开关误差。3)在存在热噪声和缺陷的情况下，对skyrmion介导的磁化动力学进行严格的建模，以了解为什么中间skyrmion状态使磁化反转变得稳健，并进一步研究这些器件的缩放。在这个项目中，学生将学习互补薄膜生长、纳米制造、磁性表征和微磁性建模。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

State of the art magnetic memory devices use electrical current to switch the magnetization of a nano-magnet from 'up' to 'down' state or vice versa and thus encode the binary bits 1 and 0 respectively. Unlike devices based on widely-used CMOS (Complementary Metal Oxide Semiconductor) technology, such a device, based on technology called spin transfer torque random access memory (STT-RAM), is non-volatile, a significant advantage. However, these devices consume about 1000 times the energy that CMOS devices use for switching. If electrical field is used to control magnetization, these devices could be a hundred times more energy-efficient. However, development of such control methods are impeded by the level of errors introduced due to the presence of material defects and room temperature thermal noise in the material. This project seeks to demonstrate new techniques that makes the switching and control process robust to such defects, thus achieving the energy savings needed for this technology to be competitive with CMOS devices. The project would also help mentor undergraduate summer research, various K-12 workshops on nano-magnetic computing. This project aims to demonstrate that forcing the magnetization through an intermediate so-called "magnetic skyrmion state", where the magnetization spirals from pointing up/down at the core to pointing down/up at the periphery of a circular nano-magnet, makes the switching process extremely robust as well as eliminates the need for any extra magnetic field. The development of such device, if successful, could make the energy efficient Voltage Control of Magnetic Anisotropy (VCMA) switching technique viable for practical memory devices while needing only modest changes to existing STT-RAM fabrication process. The key technical approach in this research project will address gaps in knowledge as well as demonstrate a proof of concept for skyrmion mediated nano-magnetic memory device. The project plans to 1) investigate the growth of various material systems and interfaces and characterize their magnetic properties to develop an optimized memory device that is energy efficient, scalable and has low switching error, 2) demonstrate proof of concept VCMA switching of a nano-magnetic memory cell ~100 nm diameter mediated by a skyrmion state and characterize its switching error, and 3) perform rigorous modeling of skyrmion mediated magnetization dynamics in the presence of thermal noise and defects to understand why the intermediate skyrmion state makes the magnetization reversal robust and study further scaling of these devices. Students will be trained on complementary thin film growth, nano-fabrication, magnetic characterization and micromagnetic modeling in this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.