Electronic devices enabled by magnon transfer torques

用于信息存储和记忆的自旋电子器件依赖于对纳米级磁性材料磁化方向的有效控制。在目前的装置中，传导电子的自旋和电荷提供了转换磁化状态所需的角动量和能量。然而，快速开关所需的电流密度仍然过高，并且与电流焦耳加热相关的能量消耗使下一代基于自旋的存储器具有挑战性。这个建议是探索替代角动量载流子，被称为磁振子，以实现磁化开关与更少的能量消耗。磁振子是一种准粒子，具有与电子自旋相同的角动量，但不带电荷。因此，当磁振子在磁性材料中运动时，没有焦耳加热。最近，有一些小组和PI已经证明，磁振子也可以作为主动角动量载流子，能够操纵磁化状态。本提案将从理论上研究磁振子运动在许多原型磁性结构和材料中的影响。目标是确定控制磁振子驱动的磁化开关的物理过程。如果成功，人们将利用磁振子作为信息操纵器，创造出一种破坏性的自旋电子设备，与传导电子的自旋相比，它的能量效率要高得多。该提案的教育部分包括研究生参与研究、培训和参观工业研究实验室，以及PI开发与该研究项目相关的自旋电子学课程。类似于电子自旋电流将移动电子的自旋角动量转移到局部磁化，称为自旋转移扭矩，磁振子电流也可以有效地将磁振子角动量转移到磁织构，从而导致磁构型的变化。本课题将探讨磁振子传递力矩（MTT）的理论基础，预测MTT驱动的磁化开关和动力学的合理结构，并提出MTT应用的器件概念。本文旨在从理论上研究磁异质结构中非平衡磁振子的产生、传播和探测，从而推动自旋电子学的发展。磁振子是由磁性有序织构（包括铁磁体、反铁磁体和铁磁体）承载的低能激发。科学问题将被解决，包括产生大MTT的物理和关键材料参数，由MTT驱动的磁化动力学，以及MTT与STT在磁性隧道结等器件中的开关效率。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。

Spin-based electronic devices for information storage and memory rely on the efficient control of magnetization orientation of nanoscale magnetic materials. At present-day devices, spins and charges of the conduction electrons provide the angular momentum and the energy needed for the switching of magnetization states. However, the current density required for fast switching remains undesirably high and the energy consumption associated with the Joule heating of the electric current makes next-generation spin-based memories challenging. This proposal is to explore alternative angular momentum carriers, known as magnons, to achieve magnetization switching with far less energy consumption. Magnons are quasi-particles that possess same amount of angular momentum as electron spins, but without electric charge. Therefore, there is no Joule heating when magnons travel in magnetic materials. Recently, there are a number of groups and the PI have demonstrated that magnons can also serve as active angular momentum carriers that are capable of manipulating magnetization states. This proposal will theoretically investigate the effects of magnon motion in a number of prototype magnetic structure and materials. The goal is to identify physical processes that govern the magnon-driven magnetization switching. If successful, one would create a disruption spintronic devices by using magnons as an information manipulator which is far more energy efficient, compared to spins of conduction electrons. The educational components of the proposal include strong graduate student participations in research, training, and visiting industrial research laboratories, as well as for PI to develop a spintronics course related to this research project.Similar to the electron spin current that transfers the spin angular momentum of mobile electrons to local magnetization, known as spin-transfer torques, magnon currents can efficiently transfer magnon angular momentum to magnetic texture as well, leading to magnetic configuration changes. This proposal will explore theoretical foundation of this magnon transfer torques (MTT), predict plausible structure for MTT driven magnetization switching and dynamics, and propose device concepts for MTT applications. The present proposal aims at advancing the field of spintronics by theoretically investigating the generation, propagation, and detection of non-equilibrium magnons in magnetic heterostructure. Magnons are low-energy excitations hosted by magnetically ordered texture (including ferrro-, antiferro- and ferri-magnets). The scientific issues will be addressed, include the physics and key materials parameters that give rise large MTT, magnetization dynamics driven by MTT, and the switching efficiency of MTT compared to that of STT in devices such as magnetic tunnel junctions.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.