Antiferromagnetic devices for spintronic memory applications

用于自旋电子存储应用的反铁磁器件

• 批准号: EP/P019749/1
• 负责人: Bryan Gallagher
• 金额: $ 56.67万
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FP019749%2F1
• 关键词: Antiferromagnetic; devices; spintronic; memory; applications

Almost all modern electronic devices require memory devices for large scale data storage with the ability to write, store and access information. There are strong commercial drives for increased speed of operation, energy efficiency, storage density and robustness of such memories. Most large scale data storage devices, including hard drives, rely on the principle that two different magnetization orientations in a ferromagnet represent the "zeros" and "ones". By applying a magnetic field to a ferromagnet one can reversibly switch the direction of its magnetisation between different stable directions and read out these states / bits from the magnetic fields they produce. This is the basis of ferromagnetic media used from the 19th century to current hard-drives. Today's magnetic memory chips (MRAMs) do not use magnetic fields to manipulate magnetisation with the writing process done by current pulses which can reverse magnetisation directions due to the spin-torque effect. In the conventional version of the effect, switching is achieved by electrically transferring spins from a fixed reference permanent magnet. More recently, it was discovered that the spin torque can be triggered without a reference magnet, by a relativistic effect in which the motion of electrons results in effective internal magnetic fields. Furthermore the magnetisation state is read electrically in such MRAMs. Therefore the sensitivity of ferromagnets to external magnetic fields and the magnetic fields they produce are not utilised. In fact they become problems since data can be can be accidentally wiped by magnetic fields, and can be read by the fields produced making data insecure. Also the fields produced limit how closely data elements can be packed.Recently we have shown that antiferromagnetic materials can be used to perform all the functions required of a magnetic memory element. Antiferromagnets have the north poles of half of the atomic moments pointing in one direction and the other half in the opposite direction leading to no net magnetisation and no external magnetic field. For antiferromagnets with specific crystal structures we predicted and verified that current pulses produce effective field which can rotate the two types of moments in the same directions. We were able to reverse the moment orientation in antiferromagnets by a current induced torque and to read out the magnetisation state electrically.Since antiferromagnets do not produce a net magnetic field they do not have all the associated problems discussed above. The dynamics of the magnetisation in antiferromagnets occur on timescales orders of magnitude faster than in ferromagnets, which could lead to much faster and more efficient operations. Finally, the antiferromagnetic state is readily compatible with metal, semiconductor or insulator electronic structures and so their use greatly expands the materials basis for such applications.This proposal aims to develop a detailed understanding of current induced switching in antiferromagnets though a program of research extensive experimental and theoretical studies and to pave the way to exploitation of this effect in future magnetic memory technologies. We will develop high quality antiferromagnetic materials and smaller and faster devices. We aim to achieve devices in which the antiferromagnetic state has not disordered (single domain behaviour) which will have improved technical parameters and which will be ideal for advancing fundamental understanding. We also aim to demonstrate and study the manipulation of regions of antiferromagnets in which there is a transition between two types of moment orientation (domain walls) using current-induced torques. As well as electrical measurements we will directly study the magnetic order in the antiferromagnetic devices using X-ray imaging techniques and we will carry out extensive theoretical modelling.

几乎所有的现代电子设备都需要具有写入、存储和访问信息的能力的用于大规模数据存储的存储器设备。对于提高此类存储器的运行速度、能源效率、存储密度和鲁棒性来说，存在强大的商业驱动力。大多数大规模数据存储设备，包括硬盘驱动器，依赖于铁磁体中的两个不同磁化方向表示“0”和“1”的原理。通过向铁磁体施加磁场，可以在不同的稳定方向之间可逆地切换其磁化方向，并从它们产生的磁场中读出这些状态/位。这是从19世纪到目前硬盘驱动器使用的铁磁介质的基础。今天的磁存储器芯片（MRAM）不使用磁场来操纵磁化，写入过程由电流脉冲完成，由于自旋扭矩效应，电流脉冲可以反转磁化方向。在该效应的传统版本中，通过从固定的参考永磁体电转移自旋来实现切换。最近，人们发现自旋力矩可以在没有参考磁体的情况下被触发，通过相对论效应，其中电子的运动导致有效的内部磁场。此外，在这种MRAM中，磁化状态被电读取。因此，没有利用铁磁体对外部磁场及其产生的磁场的敏感性。事实上，它们成为问题，因为数据可能会被磁场意外擦除，并且可以通过产生的磁场读取，从而使数据不安全。此外，所产生的磁场限制了数据元素的紧密程度。最近，我们已经证明，反铁磁材料可以用来执行磁存储器元件所需的所有功能。反铁磁体具有一半原子磁矩的北极指向一个方向，另一半指向相反方向，导致没有净磁化强度和没有外部磁场。对于具有特定晶体结构的反铁磁体，我们预测并验证了电流脉冲产生的有效场可以使两种磁矩向同一方向旋转。我们能够通过电流感应的力矩来反转反铁磁体的磁矩取向，并用电读出磁化状态，因为反铁磁体不产生净磁场，所以它们不存在上面讨论的所有相关问题。反铁磁体中的磁化动力学发生在比铁磁体快几个数量级的时间尺度上，这可能导致更快和更有效的操作。最后，反铁磁状态是很容易兼容的金属，半导体或绝缘体的电子结构，所以他们的使用大大扩展了材料基础，为这样的应用程序。本建议旨在通过广泛的实验和理论研究的研究计划，发展一个详细的了解电流感应开关在反铁磁体，并铺平了道路，利用这种效果在未来的磁存储技术。我们将开发高质量的反铁磁材料和更小更快的设备。我们的目标是实现设备中的反铁磁状态没有无序（单畴行为），这将有改进的技术参数，这将是理想的推进基本的理解。我们还旨在展示和研究反铁磁体区域的操纵，其中有两种类型的力矩取向（畴壁）之间的过渡，使用电流引起的扭矩。以及电气测量，我们将直接研究磁秩序的反铁磁器件使用X射线成像技术，我们将进行广泛的理论建模。

项目成果

Antiferromagnetic CuMnAs multi-level memory cell with microelectronic compatibility.

• DOI: 10.1038/ncomms15434
• 发表时间: 2017-05-19
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Olejník K;Schuler V;Marti X;Novák V;Kašpar Z;Wadley P;Campion RP;Edmonds KW;Gallagher BL;Garces J;Baumgartner M;Gambardella P;Jungwirth T
• 通讯作者: Jungwirth T

Terahertz electrical writing speed in an antiferromagnetic memory.

• DOI: 10.1126/sciadv.aar3566
• 发表时间: 2018-03
• 期刊: Science advances
• 影响因子: 13.6
• 作者: Olejník K;Seifert T;Kašpar Z;Novák V;Wadley P;Campion RP;Baumgartner M;Gambardella P;Němec P;Wunderlich J;Sinova J;Kužel P;Müller M;Kampfrath T;Jungwirth T
• 通讯作者: Jungwirth T

Quenching of an antiferromagnet into high resistivity states using electrical or ultrashort optical pulses

• DOI: 10.1038/s41928-020-00506-4
• 发表时间: 2020-11-30
• 期刊: NATURE ELECTRONICS
• 影响因子: 34.3
• 作者: Kaspar, Z.;Surynek, M.;Jungwirth, T.
• 通讯作者: Jungwirth, T.

Electrically induced and detected Néel vector reversal in a collinear antiferromagnet.

• DOI: 10.1038/s41467-018-07092-2
• 发表时间: 2018-11-08
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Godinho J;Reichlová H;Kriegner D;Novák V;Olejník K;Kašpar Z;Šobáň Z;Wadley P;Campion RP;Otxoa RM;Roy PE;Železný J;Jungwirth T;Wunderlich J
• 通讯作者: Wunderlich J

Probing the manipulation of antiferromagnetic order in CuMnAs films using neutron diffraction

• DOI: 10.1063/5.0103390
• 发表时间: 2022-08
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: S. Poole;L. X. Barton;M. Wang;P. Manuel;D. Khalyavin;S. Langridge;K. Edmonds;R. Campion;V'it Nov'ak;P. Wadley