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

现有技术的磁存储器设备使用电流来将纳米磁体的磁化从"上"状态切换到"下"状态，或者反之亦然，并且因此分别对二进制位1和0进行编码。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，这种基于称为自旋转移矩随机存取存储器（STT-RAM）的技术的器件是非易失性的，这是一个显著的优点。然而，这些器件消耗的能量大约是CMOS器件用于开关的能量的1000倍。如果使用电场来控制磁化，这些设备的能效可以提高一百倍。然而，这种控制方法的发展受到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的阻碍。该项目旨在展示新技术，使开关和控制过程对这些缺陷具有鲁棒性，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夏季研究，各种K-12研讨会（包括与工程计划中的里士满少数民族合作为代表性不足的部分提供K-12研究经验）。该项目旨在证明，迫使磁化通过一个中间所谓的“磁skyrmion状态”，其中磁化螺旋从指向上/下在核心指向下/上在圆形纳米磁体的外围，使切换过程非常鲁棒，以及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，可以使磁各向异性（VCMA）开关技术的节能电压控制可行的实际存储器设备，而只需要适度的变化，现有的STT-RAM的制造工艺。该研究项目的关键技术方法将解决知识差距，并证明skyrmion介导的纳米磁记忆器件的概念证明。该项目计划1）研究各种材料系统和界面的生长，并表征其磁特性，以开发一种节能，可扩展且具有低切换误差的优化存储器器件，2）演示由skyrmion状态介导的纳米磁性存储器单元~100 nm直径的VCMA切换的概念证明，并表征其切换误差，以及3）在存在热噪声和缺陷的情况下执行Skyrmion介导的磁化动力学的严格建模，以理解为什么中间Skyrmion状态使得磁化反转稳健，并研究这些器件的进一步缩放。学生将在该项目中接受互补薄膜生长、纳米制造、磁性表征和微磁建模方面的培训。该奖项反映了NSF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 (including a K-12 research experience for underrepresented sections in partnership with Richmond Minorities in Engineering Program) 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.