Voltage controlled antiferromagnetism in magnetic tunnel junctions

磁隧道结中的压控反铁磁性

• 批准号: 1905783
• 负责人: Weigang Wang
• 金额: $ 42.96万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1905783&HistoricalAwards=false
• 关键词: Voltage; controlled; antiferromagnetism; magnetic; tunnel

Non-technical Abstract:An effective way to influence the magnetic properties of a thin film is by using electric fields, which may lead to many new functionalities in future generations of electronic devices. In most cases, this type of electric control of magnetic order is investigated in ferromagnetic (FM) systems. For example, both the preferred direction of magnetization and the size of magnetization of a Fe or Co thin film can be modified by voltages applied on adjacent dielectric layers. Indeed, this effect has been successfully used to manipulate the resistance of a magnetic tunnel junctions (MTJ), a sandwich structure where the tunneling probability of electrons across an insulting barrier depends on the relative orientations of the magnetizations of the two FM films on both sides of the insulator, to achieve a small switching energy that is below 10 fJ. In this project, the principal investigator explores the voltage-controlled magnetic properties in antiferromagnetic (AF) systems. Antiferromagnets have a number of advantages compared with the their FM counterparts: they have no net magnetization therefore AF cells can be packed into extremely high density without affecting each other; for the same reason, they are immune to external magnetic fields; due to the staggered arrangement of spins in antiferromagnets, the spin currents can possibly penetrate much deeper; and most importantly, the intrinsic magnetization switching frequency of antiferromagnets can be in the THz region, promising ultra-high speed operations as well as reduced switching energy. This project incorporates the education and training of graduate/undergraduate students and high school students, especially those belonging to underrepresented groups, in all stages of the research. In addition, outreach to general public will be carried out through activities such as Physics Phun Night and Physics Open House.Technical Abstract:This project aims to explore voltage-controlled antiferromagnetism in MTJs with AF barriers, and in MTJs with the spin-filtering tunneling effect where the magnetoresistance is driven by the AF/FM coupling. In the first research topic, perpendicular MTJs with AF barriers such as Chromium(III) oxide are fabricated, where the insulating layer serves as both the tunnel barrier and the AF material. The exchange bias of the AF materials and the voltage-controlled AF order can be very sensitively detected by the sharp transitions of the perpendicular tunneling magnetoresistance curves measured under different bias voltages. The ability to grow high quality thinfilm heterostructure with extremely small roughness, as well as the fabrication of perpendicular MTJ samples with sub-100nm lateral dimension will enable, for the first time, the investigation of many intrinsic properties with less parasitic effects associated with grain boundaries and defects in the AF layer. In the second research topic, the spin-filtering tunneling effect with the newly discovered 2 dimensional (2D) materials as barriers will be explored. Different 2D materials are incorporated with various nonmagnetic electrodes to facilitate the understanding of the very large TMR. The effort will be focused on voltage-controlled AF/FM coupling in 2D barriers, which can potentially lead to very efficient switching of MTJs. These research activities will not only add significantly to our understanding of voltage-controlled antiferromagnetism, but also benefit applications such as MRAM, spin logic, spintronic oscillators, and neuromorphic processors.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.

非技术摘要：影响薄膜磁性特性的有效方法是使用电场，这可能会导致许多新功能在后代的电子设备中。在大多数情况下，在铁磁（FM）系统中研究了这种对磁性的电力控制。例如，磁化的首选方向和Fe或Co薄膜的磁化大小都可以通过在相邻介电层上施加的电压来修饰。实际上，这种效果已成功地用于操纵磁性隧道连接（MTJ）的电阻，这是一种三明治结构，其中电子跨侮辱性屏障的隧道概率取决于隔离器两侧的两个FM膜的相对取向，以达到隔热器两侧的磁化率，以达到低于10 fj的小开关能量。在该项目中，主要研究人员探讨了抗铁磁（AF）系统中的电压控制的磁性。与FM的同类产品相比，抗铁磁铁具有许多优势：它们没有净磁化，因此AF细胞可以将其填充成极高的密度而不会相互影响。出于同样的原因，它们不受外部磁场的影响。由于抗铁磁体中旋转的交错排列，旋转电流可能会更深地穿透。最重要的是，抗铁磁铁的内在磁化切换频率可以在THZ区域，有望实现超高速度操作以及降低开关能量。该项目将研究生/本科生和高中生的教育和培训（尤其是属于代表性不足群体的学生）的教育和培训。此外，将通过诸如Phun Night和Physics Open House之类的活动进行向公众进行外向。技术摘要：该项目旨在探索具有AF障碍的MTJ的电压控制的反铁磁性，以及MTJ在MTJ中，具有磁性隧道效应的磁场效应，该磁力效果由Af/affirative af/five fired fired。在第一个研究主题中，制造了具有AF障碍（III）等AF屏障的垂直MTJ，在该障碍物（III）氧化物中被制造，绝缘层用作隧道屏障和AF材料。通过在不同偏置电压下测得的垂直隧穿磁磁曲线的急剧过渡，可以非常灵敏地检测AF材料的交换偏置和电压控制的AF顺序。具有极小粗糙度的高质量薄膜异质结构的能力，以及垂直的MTJ样品的制造具有近100nm横向尺寸的垂直MTJ样品将首次启用许多内在特性，这些内在特性与AF层中粒度边界和缺陷相关的许多寄生效应较少。 在第二个研究主题中，将探索具有新发现的2维（2D）材料作为障碍的自旋过滤隧道效应。 不同的2D材料与各种非磁性电极合并，以促进对非常大的TMR的理解。这项工作将集中在2D屏障中的电压控制的AF/FM耦合上，这可能会导致MTJ的非常有效的切换。这些研究活动不仅将大大增加我们对电压控制的防铁磁性的理解，而且还使MRAM，Spin Logic，Spintronic振荡器和神经形态处理器等应用有益于应用。这奖反映了NSF的立法任务，并被认为是通过基金会的智力优点和广泛的评估来进行评估，并值得通过评估来进行评估。

项目成果

Perpendicular magnetic tunnel junctions with multi-interface free layer

• DOI: 10.1063/5.0066782
• 发表时间: 2021-12-13
• 期刊: APPLIED PHYSICS LETTERS
• 影响因子: 4
• 作者: Khanal, Pravin;Zhou, Bowei;Wang, Weigang
• 通讯作者: Wang, Weigang

On the temperature-dependent characteristics of perpendicular shape anisotropy-spin transfer torque-magnetic random access memories

垂直形状各向异性-自旋转移矩-磁随机存取存储器的温度相关特性

• DOI: 10.1063/5.0054356
• 发表时间: 2021
• 期刊: Journal of Applied Physics
• 影响因子: 3.2
• 作者: Zhang, Wei;Tong, Zihan;Xiong, Yuzan;Wang, Weigang;Shao, Qiming
• 通讯作者: Shao, Qiming