Pt/Co/Au多层膜中磁斯格明子的密度调控

Pt/Co/Au多层膜中磁斯格明子的密度调控

徐  琦，张宇中，胡  玥，李泽林，姜  泽，王  楠，蒙  萱，邓  霞，关超帅，朱  柳，张军伟^*，彭  勇^*

(兰州大学材料与能源学院兰州大学物理与科学技术学院 兰州大学电镜中心，磁学与磁性材料教育部重点实验室，甘肃 兰州 730000)

摘   要    磁斯格明子是一种拓扑自旋结构，凭借其尺寸小、结构稳定和驱动电流密度低等特性，有望成为新一代赛道磁存储器件的信息存储单元。在存有磁斯格明子的材料体系中，具有界面Dzyaloshinskii-Moriya Interaction（DMI）的铁磁多层膜可与现代纳米制造工艺兼容，并且这种铁磁多层膜产生的磁斯格明子在室温下可稳定存在，这为基于磁斯格明子研发的电子器件提供了材料基础。然而磁性多层膜中界面DM相互作用、交换相互作用和偶极相互作用等各种作用之间的竞争，导致了磁斯格明子密度的随机变化，降低了磁斯格明子器件的可控性。因此，系统的研究材料参数对磁斯格明子密度的调控具有重要的意义。本文通过改变磁性层Co层的厚度调控了磁性多层膜中磁斯格明子的密度。实验结果表明，随着Co层厚度的增加，磁斯格明子的密度先增加后减少，其中Co层为2.1 nm时磁斯格明子密度最大。理论计算表明，磁性层厚度的变化会引起磁各向异性的转变和内禀属性DM相互作用的改变，进而影响磁斯格明子密度的变化。

关键词     磁斯格明子；球差电镜；洛伦兹技术；磁性层厚度
中图分类号：O44；O469；TG115.21⁺5.3   文献标识码：A       doi:10.3969/j.issn.1000-6281.2024.02.004

Density modulation of magnetic skyrmions in Pt/Co/Au multilayers

XU Qi,ZHANG Yuzhong, HU Yue, LI Zelin, JIANG Ze, WANG Nan, MENG Xuan, DENG Xia,

GUAN Chaoshuai, ZHU Liu, ZHANG Junwei *, PENG Yong *

(School of Materials and Energy, School of Physical Science and Technology, Electron Microscopy Centre of Lanzhou University and Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou Gansu 730000, China)

Abstract    Magnetic skyrmion has a topological spin texture, which possesses many excellent features such as small size, stable structure and low drive current density. It has great potential application in information storage and information processing. Ferromagnetic multilayer films with interfacial DMI can be compatible with modern nanocrystalline manufacturing processes in the material system with magnetic skyrmions. Magnetic skyrmions generated in the ferromagnetic multilayer films can be stable at room temperature, which is important for developing electronic devices based on magnetic skyrmions.However, due to the competing interfacial DM interactions, magnetic anisotropy, exchange interactions and dipole interactions in magnetic multilayers, the generation of magnetic skyrmions lacks regularity and has a low density. The systematic tuning of material parameters to generate high density magnetic skyrmions at room temperature in magnetic multilayers is the key step to solve this problem. Here, a series of Pt/Co/Au multilayers with different Co layer thicknesses were prepared by magnetron sputtering. Their magnetic anisotropy was qualitatively analyzed using hysteresis lines obtained from a vibrating sample magnetometer (VSM). Their magnetic domain structure was imaged using the Lorentzian mode of transmission electron microscopy. The results showed that the density of magnetic skyrmions increased and then decreased as the Co layer thickness increases, with the maximum density of magnetic skyrmions at a Co layer of 2.1 nm. Theoretical calculations showed that the change in the thickness of the magnetic layer caused a shift in the magnetic anisotropy and a change in the endogenous property Dzyaloshinskii-Moriya interaction D, which in turn affected the change in the magnetic skyrmions density.

Keywords    magnetic skyrmions; spherical electron microscopy; Lorentz technique, in situ thermal pole;magnet layer thickness

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