Chiral Spin Textures in Magnetic Nanostructures

摘要：磁体中的磁矩可以形成称为自旋织构的各种构型，例如畴壁，其中磁矩形成绕组构型，连接具有不同磁化方向的相邻畴。通常，自旋纹理中矩的旋转感觉被认为是非手性的，其中左旋和右旋是同样可能的。在某些磁性薄膜中，磁性层与重金属层界面处原子结构的反转对称性被打破，导致界面效应，从而提升了手性简并并稳定了自旋螺旋、手性畴壁或磁天幕等手性自旋结构。这些手性自旋织构表现出优先的手性和迷人的拓扑特征。它们的非凡性质为研究磁学的基本问题提供了新的见解，并为新型磁技术提供了激动人心的潜力。该项目旨在通过解锁一些自由度来更好地理解和控制这种自旋纹理，从而显著推进该领域的发展。研究了几种新的自旋织构，包括二维薄膜中的奇异类型的skyrmions和手性畴壁，以及三维磁性结构中的拓扑自旋织构，如Mobius带。它们有可能从根本上改变未来信息存储的能源格局。该项目为学生提供了在大学以及国家实验室等设施的宝贵培训机会。首席研究员通过开设课程、公开讲座、交流访问和专业会议组织，积极参与各种努力，以扩大代表性不足群体的参与。技术摘要：研究手性自旋织构，展示了一些新的自由度，以更好地控制它们，包括反斯基米子霍尔角、拓扑数、化学吸收物质和三维拓扑构型。利用各向异性Dzyaloshinskii-Moriya相互作用稳定磁性薄膜中的反粒子。研究了反skyrmion霍尔角用于控制skyrmion轨迹或拓扑排序，可用于设计复杂的skyrmion器件。高绕组数skyrmions被证明，它解锁的拓扑数作为一个新的自由度，可能支持新的拓扑功能的逻辑器件。研究了真空条件下化学吸附物质对铁磁薄膜的影响，以诱导手性畴壁，实现无磁场或电场的直接写入。研究了低原子序数原子和有机分子的化学吸附，诱导了磁性手性的可逆开关和垂直磁各向异性的调谐。制备了新型的三维拓扑自旋织构，如莫比乌斯带，并研究了它们的拓扑特性。这些新颖的自旋结构为稳健和低耗散的信息存储提供了新的机制，这与未来纳米电子学的重大挑战是一致的。该项目包括各种各样的努力，以扩大代表性不足群体的参与。参与的学生将有机会接触到学术界、政府实验室和其他研究机构的研究经验。这项DMR拨款支持磁性纳米粒子的手性自旋结构研究，资金来自数学和物理科学理事会材料研究部的凝聚态物理（CMP）和电子和光子材料（EPM）项目。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。

Nontechnical Abstract:Magnetic moments in magnets can form various configurations known as spin textures, such as domain walls where the moments form a winding configuration connecting adjacent domains with different magnetization directions. Usually, the rotational sense of the moments in spin textures is expected to be achiral, where the left- and right-handed rotations are equally possible. In certain magnetic thin films, the broken inversion symmetry of atomic structure at the interface between magnetic and heavy metal layers leads to an interfacial effect which lifts the chiral degeneracy and stabilizes chiral spin structures such as spin spirals, chiral domain walls or magnetic skyrmions. These chiral spin textures exhibit a preferred handedness and fascinating topological characteristics. Their extraordinary properties provide new insights into fundamental problems of magnetism and exciting potentials for novel magnetic technologies. This project aims at significantly advancing the field by unlocking a number of degrees of freedom for a better understanding and control of such spin textures. Several novel spin textures are investigated, including exotic types of skyrmions and chiral domain walls in 2-dimensional thin films and topological spin textures such as Mobius bands in 3-dimensional magnetic structures. They have the potential to fundamentally transform the energy landscape for future information storage. This project provides valuable training opportunities for students in university as well as national laboratory and other facilities. The principal investigator actively engages in a variety of efforts to broaden participation from underrepresented groups through course offering, public lectures, exchange visits, and professional conference organization.Technical Abstract:Chiral spin textures are investigated to demonstrate a number of new degrees of freedom to better control them, including antiskyrmion Hall angle, topological number, chemisorbed species, and 3-dimensional topological configuration. Anisotropic Dzyaloshinskii-Moriya interaction is utilized to stabilize antiskyrmions in magnetic thin films. The antiskyrmion Hall angle is explored for controlling skyrmion trajectory or topological sorting, which can be potentially used for designing complex skyrmionics devices. High winding number skyrmions are demonstrated, which unlocks the topological number as a new degree of freedom that may support novel topological functionalities in logic devices. Effects of chemisorbed species under vacuum onto ferromagnet films are studied to induce chiral domain walls and enable direct writing of skyrmions without magnetic or electric fields. Chemisorptions of low atomic number atoms and organic molecules are studied to induce reversible switching of magnetic chirality and tuning of perpendicular magnetic anisotropy. Novel types of 3-dimensional topological spin textures such as Mobius bands are fabricated and their topological characters are investigated. These novel spin textures offer new mechanisms for robust and low dissipation information storage, which is well aligned with grand challenges for future nanoelectronics. This project includes a wide variety of efforts to broaden participation from underrepresented groups. Students involved receive excellent exposure to research experience in academia, government laboratory and other research facilities.This DMR grant supports research on chiral spin structure in magnetic nanoparticles with funding from the Condensed Matter Physics (CMP) and the Electronic and Photonic Materials (EPM) Programs in the Division of Materials Research of the Mathematical and Physical Sciences Directorate.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.