CAREER: Low-Loss Spintronic Devices with Vertically Engineered Magnets

职业：具有垂直设计磁体的低损耗自旋电子器件

• 批准号: 2144333
• 负责人: Satoru Emori
• 金额: $ 50万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2144333&HistoricalAwards=false
• 关键词: CAREER; Low; Loss; Spintronic; Devices

In personal computers and data centers, information is often stored in magnetic films where the two digital states (“0” and “1”) are represented by opposite magnetization directions. Switching the magnetization with low loss (minimal wasted energy) is key to developing energy-efficient digital memory devices. In recent years, an effect called “spin-orbit torque” has been envisioned as a promising way to switch next-generation magnetic memories. However, the outstanding problem is that stronger spin-orbit torques require extremely thin, lossy magnetic films, in which switching involves a large amount of wasted energy. The proposed research will resolve this longstanding problem by developing a new family of magnetic films with tailored chemical composition profiles, which simultaneously enable strong spin-orbit torques and low loss. A successful outcome of this research will improve the energy efficiency of spin-orbit-torque magnetic memories by more than a hundredfold. In addition, research will advance the basic understanding of how spin-orbit torques and losses arise in magnetic materials, with broader applications in not only digital memories but also brain-inspired and quantum computing technologies. Moreover, it is proposed to develop a hands-on in-class activity for elementary school students to build audio speakers with inexpensive materials. This activity will help students develop a long-lasting appreciation for how the physical concepts of electricity, magnetism, and sound apply to everyday technologies. Spin-orbit torque (SOT) devices for memory and computing applications are typically bilayers, consisting of a magnetic film interfaced with a spin-orbit material. The problem with this device structure is that stronger SOTs require thinner magnets with thicknesses down to ~1 nm, but thinner magnets exhibit higher damping that results in high power consumption and poor performance. The proposed research will address this longstanding problem by simultaneously engineering strong SOTs and low damping in several-nm-thick, single-layer magnetic metal films. The research will take a fundamentally different approach to symmetry breaking, which is an essential ingredient for the emergence of SOTs. Specifically, in contrast to the conventional bilayers where symmetry is broken at film interfaces, the proposed approach deliberately breaks symmetry within the magnetic film itself – via a continuous compositional gradient along the thickness axis. Such bulk symmetry breaking is hypothesized to yield strong SOTs directly within a thick, low-damping magnetic film. The objectives of this research are to: (1) grow and characterize vertically graded magnetic films and determine how their compositions and structures impact SOTs and damping; and (2) quantify how the SOTs and damping of vertically graded magnets impact the performance of spintronic memories, oscillators, and spin-wave channels. A successful outcome of this research will enable transformative advances in SOT-driven devices – including two-orders-of-magnitude lower power dissipation, along with higher stability, higher signal output, and excellent compatibility with commercial fabrication processes. More broadly, this research will catalyze device development that leverages spin-orbit phenomena in graded materials, which have the potential to supersede heterostructures relying on atomically sharp interfaces.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.

在个人计算机和数据中心中，信息通常存储在两个数字状态（“ 0”和“ 1”）的磁性膜中，以相反的磁化方向表示。用低损耗（最小浪费能量）切换磁力化是开发节能数字记忆设备的关键。近年来，已将称为“自旋轨道扭矩”的效果被设想为切换下一代磁性记忆的一种承诺方式。但是，出色的问题是，强的自旋轨道扭矩需要极度薄，有损的磁性膜，其中开关涉及大量浪费能量。拟议的研究将通过开发具有量身定制的化学成分曲线的新的磁性薄膜系列来解决这个长期存在的问题，从而使强大的自旋轨道扭矩和低损失能够。这项研究的成功结果将提高自旋轨道磁性记忆的能源效率超过一百倍。此外，研究将进一步了解磁性材料中旋转轨道和损失的基本理解，不仅在数字记忆中，而且在大脑启发和量子计算技术中都有更广泛的应用。此外，有人建议开发一项动手活动，以供小学生使用便宜的材料来建造音频扬声器。这项活动将有助于学生对电力，磁性和声音的物理概念如何适用于每天的技术，并为学生提供长期的欣赏。用于内存和计算应用的自旋轨道扭矩（SOT）设备通常是双层，由与自旋轨道材料相连的磁性膜组成。这种设备结构的问题在于，强SOT需要更薄的磁铁，厚度低至约1 nm，但较薄的磁体暴露了更高的阻尼，从而导致高功耗和性能差。拟议的研究将通过简单地设计强SOT并在几米厚的单层磁性金属膜中进行较低的阻尼来解决这个长期存在的问题。这项研究将采取一种根本不同的对称性破坏方法，这对于SOT的出现是必不可少的。具体而言，与在膜界面上打破对称性的传统双层相比，提出的方法故意通过沿厚度轴的连续复合梯度在磁性膜本身中打破对称性。假设这种散装的对称性破裂可以直接在厚，低阻尼的磁性膜中产生强SOT。这项研究的目标是：（1）生长和表征垂直分级的磁性膜，并确定它们的组成和结构如何影响SOT和舞蹈； （2）量化垂直分级磁体的SOT和阻尼如何影响自旋记忆，振荡器和自旋波通道的性能。这项研究的成功结果将在SOT驱动的设备中实现变革性的进步，包括降低功率降低功率降低，以及较高的稳定性，更高的信号输出以及与商业制造过程的出色兼容性。从更广泛的角度来看，这项研究将催化设备开发，以利用分级材料中的旋转轨道现象，这些材料有可能取代依靠原子上尖锐界面的异质结构。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子和更广泛的影响来评估CRITEIA CRITERIA。

项目成果

Quantifying the orbital-to-spin moment ratio under dynamic excitation

量化动态激励下的轨道与自旋矩比

• DOI: 10.1063/5.0198326
• 发表时间: 2024
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Emori, Satoru;Maizel, Rachel E.;Street, Galen T.;Jones, Julia L.;Arena, Dario A.;Shafer, Padraic;Klewe, Christoph
• 通讯作者: Klewe, Christoph