Current-driven domain wall motion and magnetomemristance in FeRh-based nanostructures

FeRh 基纳米结构中电流驱动的畴壁运动和磁阻

基本信息

批准号：
EP/M018504/1
负责人：
Christopher Marrows
金额：
$ 87.42万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FM018504%2F1
关键词：
Current driven domain wall motion

项目摘要

This project will study current-driven motion of antiferromagnetic/ferromagnetic (AF/FM) domain walls (DWs) in FeRh-based nanostructures. This will both elucidate the fundamental physics of the phase transition and also explore the potential for (magneto-)memristor devices, based on our prior demonstration of temperature/field controlled DW motion in an FeRh epilayer with a doping gradient. Memristors are devices suitable for ultradense non-volatile memory and also show many of the characteristics of an artificial synapse, opening the door to novel neuromorphic memory and logic architectures that promise enhanced functionality and low energy operation in future generations of ITC hardware. To achieve this goal we first need to know what doping materials and densities are required to control the AF-FM phase transition temperature, provide appropriate hysteresis in the transition (to store information), and largest possible resistivity change (for readout) between the AF and FM phases, as well as what parameters (materials and densities) would describe an ideal doping gradient. Next, we will need to establish how small a magnetic nanostructure can be formed from FeRh and retain a suitable AF/FM transition, and the precise conditions and requirements that permit the smallest nanostructures to be stable. Then it will be necessary to establish the current densities needed to move the domain walls that separate ferromagnetic and antiferromagnetic regions in the phase-separated regime of FeRh. Last, we will need to demonstrate a memristive action under current-driven domain wall motion in a nanostructure with a suitable doping gradient.Our project will combine state-of-the-art magnetic materials growth, characterisation, direct imaging of these novel DWs, and device fabrication and test, taking us from basic materials development to a fully operational magneto-memristor prototype nanostructure. We will begin by sputter-depositing uniformly- and gradient-doped FeRh epilayer materials and measuring their magnetic and magnetotransport properties, which will tell us the dopant materials and doping levels needed to achieve optimal memristive action. We will then fabricate nanostructures down to the few 10s of nm scale from the optimally doped FeRh layers, either as individual nanostructures (for microscopy) or as large-scale arrays of nanostructures (for magnetometry), which will reveal the minimum size at which a phase transition that is useful for memristive action is retained. Next, we will carry out world-first experiments on current-driven AF/FM domain wall motion in lateral FeRh nanowires, using magnetic microscopy to track the motion of DWs in response to current pulses, revealing the efficiency of spin injection for DW motion and the degree and nature of DW pinning arising from different sources. We will then pattern nanopillars from gradient-doped layers and study DW motion driven by a vertical current in a prototype memristor device, using both magnetotransport measurements and direct imaging of the internal structure of the device. The key result will be the magneto-memristance as a function of device size, temperature, and magnetic field. The results we shall obtain will not only lead to high impact publications and conference presentations by shedding light on the still poorly understood fundamental problem of the nature of the phase transition in FeRh, but also reveal the performance characteristics of the world's first magneto-memristor, developing potentially valuable knowhow in the field of novel neuromorphic computer architectures.

该项目将研究 FeRh 纳米结构中反铁磁/铁磁 (AF/FM) 畴壁 (DW) 的电流驱动运动。这将阐明相变的基本物理原理，并基于我们之前在具有掺杂梯度的 FeRh 外延层中进行温度/场控制的 DW 运动的演示，探索（磁）忆阻器器件的潜力。忆阻器是适用于超密集非易失性存储器的器件，并且还表现出人工突触的许多特性，为新型神经形态存储器和逻辑架构打开了大门，这些架构有望在未来几代 ITC 硬件中实现增强功能和低能耗运行。为了实现这个目标，我们首先需要知道需要什么掺杂材料和密度来控制 AF-FM 相变温度，在转变中提供适当的滞后（以存储信息），以及 AF 之间最大可能的电阻率变化（用于读出）和 FM 相位，以及哪些参数（材料和密度）可以描述理想的掺杂梯度。接下来，我们需要确定由 FeRh 形成的磁性纳米结构有多小并保持合适的 AF/FM 转变，以及允许最小纳米结构稳定的精确条件和要求。然后，有必要建立移动磁畴壁所需的电流密度，这些磁畴壁在 FeRh 的相分离区域中分隔铁磁区域和反铁磁区域。最后，我们需要在具有合适掺杂梯度的纳米结构中展示电流驱动畴壁运动下的忆阻作用。我们的项目将结合最先进的磁性材料生长、表征、这些新型 DW 的直接成像，以及器件制造和测试，使我们从基础材料开发到完全可操作的磁忆阻器原型纳米结构。我们将从溅射沉积均匀和梯度掺杂的 FeRh 外延层材料开始，并测量它们的磁性和磁输运特性，这将告诉我们实现最佳忆阻作用所需的掺杂剂材料和掺杂水平。然后，我们将从最佳掺杂的 FeRh 层中制造小至几十纳米尺度的纳米结构，无论是作为单个纳米结构（用于显微镜）还是作为大规模纳米结构阵列（用于磁力测定），这将揭示对忆阻作用有用的相变被保留。接下来，我们将在横向 FeRh 纳米线中开展世界首个电流驱动 AF/FM 畴壁运动的实验，利用磁显微镜跟踪 DW 响应电流脉冲的运动，揭示 DW 运动的自旋注入效率和不同来源产生的 DW 钉扎的程度和性质。然后，我们将利用磁输运测量和器件内部结构的直接成像，对梯度掺杂层的纳米柱进行图案化，并研究原型忆阻器器件中由垂直电流驱动的 DW 运动。关键结果将是磁忆阻与器件尺寸、温度和磁场的函数关系。我们将获得的结果不仅将通过阐明至今仍知之甚少的 FeRh 相变本质的基本问题，带来高影响力的出版物和会议演讲，而且还将揭示世界上第一个磁忆阻器的性能特征，在新型神经形态计算机架构领域开发具有潜在价值的专业知识。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Direct visualization of the magnetostructural phase transition in nano-scale FeRh thin films using differential phase contrast imaging

使用微分相差成像直接可视化纳米级 FeRh 薄膜中的磁结构相变

DOI：
10.48550/arxiv.1909.03966
发表时间：
2019
期刊：
影响因子：
0
作者：
Almeida T
通讯作者：
Almeida T

Magnetothermodynamic Properties and Anomalous Magnetic Phase Transition in FeRh Nanowires

FeRh 纳米线的磁热力学性质和反常磁相变

DOI：
10.1109/tmag.2018.2832191
发表时间：
2018
期刊：
IEEE Transactions on Magnetics
影响因子：
2.1
作者：
Matsumoto K
通讯作者：
Matsumoto K

Quantitative TEM imaging of the magnetostructural and phase transitions in FeRh thin film systems.

DOI：
10.1038/s41598-017-18194-0
发表时间：
2017-12-19
期刊：
Scientific reports
影响因子：
4.6
作者：
Almeida TP;Temple R;Massey J;Fallon K;McGrouther D;Moore T;Marrows CH;McVitie S
通讯作者：
McVitie S

Direct visualization of the magnetostructural phase transition in nanoscale FeRh thin films using differential phase contrast imaging