Electronic devices enabled by magnon transfer torques

点击翻译按钮获取中文摘要

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.