兰州大学机构库 >物理科学与技术学院
自旋轨道矩驱动人工反铁磁翻转及其在传感器中的应用
Alternative TitleSpin-Orbit Torque Induced Magnetization Switching in Synthetic Antiferromagnetic and Its Application in Sensor
罗科留
Subtype硕士
Thesis Advisor曹江伟
2023-05-27
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学硕士
Degree Discipline物理学
Keyword自旋轨道力矩 spin orbit torque 人工反铁磁 synthetic antiferromagnetic 磁阻传感器 magnetoresistance sensor 惠斯通电桥 Wheatstone-bridge
Abstract

近年来,由重金属、拓扑绝缘体和反铁磁与铁磁体形成的异质结构中的自旋轨道矩(SOT)效应已成为一种高效的操纵磁化的方法,它已成功地用于翻转磁化和驱动畴壁运动。SOT在驱动磁化翻转方面具有高速、低功耗的特性,极大地促进了自旋电子器件的发展。除了应用SOT,研究者为提高自旋电子器件的性能还积极探索新的材料体系。与传统的单一铁磁层相比,人工反铁磁结合了反铁磁的零杂散场和高热稳定性的优点,且它的反铁磁交换耦合场可达几千奥斯特,其已成为一种重要的自旋电子器件候选材料,比如人工反铁磁结构可用作磁性隧道结的自由层来提高热稳定性和降低临界翻转电流,它也可用于磁传感器的参考层以获得更大的磁场响应范围。由于SOT翻转磁化的高效性和人工反铁磁结构在应用上的优势,我们研究了人工反铁磁结构中SOT驱动的磁化翻转;进一步我们将人工反铁磁结构用作自旋阀的参考层,通过SOT驱动人工反铁磁结构磁化翻转实现了全惠斯通电桥结构的巨磁电阻传感器。主要的研究内容和结果如下:

1)制备了基于Co/Pt多层膜的垂直磁各向异性人工反铁磁(P-SAF)结构,其最大反铁磁交换耦合场可达10.7 kOe。研究了人工反铁磁结构的电流诱导磁化翻转行为,临界翻转电流密度为2.4×1011 A/m2,这与单层铁磁层的临界翻转电流密度相当。另外,我们还研究了人工反铁磁结构中电流驱动磁化翻转与外加面内辅助磁场的依赖关系,发现电流驱动磁化翻转的极性会随着辅助磁场大小的变化而发生改变。分析表明,这种异常的磁化翻转行为可以用场调制手性畴壁运动引起的不对称磁畴扩张或收缩来解释,即磁化翻转的方向仅取决于畴壁运动的相对速度。

2)在Co/Cu/Co和P-SAF/Cu/Co自旋阀结构中实现全桥传感器设置。在自旋阀底部插入重金属Pt,其产生的自旋流可以驱动参考层(Co或者P-SAF)磁化翻转。由于全桥结构中通过相邻桥臂的电流方向相反,其诱导的SOT使相邻桥臂的磁化方向相反,形成全桥传感器。该传感器对面外磁场呈线性响应,动态范围从几百到几千奥斯特。最后,我们给出了具有面外垂直线性响应和全惠斯通电桥结构的隧道磁电阻磁场传感器原型器件结构。我们认为这种器件在电流传感器和三维磁场探测方面具有很好的应用价值。

Other Abstract

In recent years, the spin-orbital torque (SOT) effect in heterostructures formed by heavy metals, topological insulators or antiferromagnets and ferromagnets has become an efficient method of manipulating magnetization, which has been successfully used to reverse magnetization and drive domain wall motion. SOT has the characteristics of high speed and low power consumption in driving magnetization switch, which greatly promotes the development of spintronic devices. In addition to the application of SOT, researchers also actively explore new material systems to improve the performance of spintronic devices. Compared with the traditional single ferromagnetic layer, the synthetic antiferromagnetic combines the advantages of zero stray field and high thermal stability of antiferromagnetic, and its antiferromagnetic exchange coupling field can reach several thousand Oe. It has become an important candidate material for spintronic devices, for example, the synthetic antiferromagnetic structure can be used as a free layer of magnetic tunnel junctions to improve thermal stability and reduce critical switch current. It can also be used in the reference layer of the magnetic sensor to obtain a larger magnetic field response range. Because of the high efficiency of SOT switch magnetization and the advantage of the synthetic antiferromagnetic structure in application, we study the magnetization reversal of the synthetic antiferromagnetic structure driven by SOT. Furthermore, we use the synthetic antiferromagnetic structure as the reference layer of spin valve and realize the giant magnetoresistance sensor of Wheatstone bridge structure by SOT driving the synthetic antiferromagnetic structure magnetization reversal. The main research contents and results are as follows:

1) Perpendicular magnetic anisotropic synthetic antiferromagnetic (P-SAF) structures based on Co/Pt multilayers were prepared, with a maximum antiferromagnetic exchange coupling field of 10.7 kOe. The current induced magnetization switch behavior of P-SAF structure is studied. The critical switch current density of P-SAF structure is 2.4 × 1011 A/m2, which is like the critical switch current density of single-layer ferromagnetic layer. In addition, we also study the dependence between current-driven magnetization switch and the auxiliary magnetic field in the external surface and find that the polarity of current-driven magnetization switch changes with the magnitude of the auxiliary magnetic field. The analysis shows that the abnormal magnetic switch behavior can be explained by modulating the asymmetric domain expansion or contraction caused by the chiral domain wall motion, that is, the direction of the magnetic switch depends only on the relative velocity of the domain wall motion.

2) Implement the full Wheatstone bridge sensor in Co/Cu/Co and P-SAF/Cu/Co spin-valve structures. The spin current generated by the heavy metal Pt inserted at the bottom of the spin valve drives the magnetization of the reference layer (Co or P-SAF) to switch, so that the magnetization direction of the adjacent bridge arms in the structure of the bridge is reversed, forming a full Wheatstone bridge sensor. The sensor shows line responses to the out-of-plane magnetic field with dynamic ranges from several hundred to thousands Oe. Finally, we present the prototype device structure of TMR magnetic field sensor with out of plane vertical linear response and full Wheatstone bridge structure. We believe that this device has good application value in current sensor and three-dimensional magnetic field detection.

Subject Area自旋电子学
MOST Discipline Catalogue理学 - 物理学
URL查看原文
Language中文
Other Code262010_220200937731
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/535219
Collection物理科学与技术学院
Affiliation
兰州大学物理科学与技术学院
Recommended Citation
GB/T 7714
罗科留. 自旋轨道矩驱动人工反铁磁翻转及其在传感器中的应用[D]. 兰州. 兰州大学,2023.
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