Enabling large tunnel magnetoresistance at room temperature in scalable epitaxial van der Waals magnet heterostructures

原子薄二维（2D）材料及其范德华（vdW）异质结构的出现引发了新的科学兴趣，为下一代技术提供了前所未有的电子特性。2D磁体是2D家族的最新成员，具有独特的特性，使其成为vdW异质结构设计的理想选择。二维磁体有可能彻底改变磁传感器和自旋电子技术，特别是隧道磁电阻（TMR）设备。这些设备在室温下提供超高灵敏度的磁场检测，使其在磁传感器，数据存储，内存和计算等应用中具有不可估量的价值。然而，可靠和可调谐的TMR器件对传统材料提出了挑战。最近的进展是利用二维磁体实现了较大的TMR值，但是大多数报告仅限于低温，研究仅限于剥离的薄片。二维磁体的可扩展生长和由隧道势垒分隔的多层磁隧道结（MTJs）的制造仍然具有挑战性，并且还未探索穿过vdW隧道势垒的相干自旋极化电子隧道对TMR效应的影响。MagicTune项目旨在通过控制扭转角和栅极电压来控制二维MTJs中的自旋极化隧道，从而在室温下实现大而可调谐的TMR，从而解决这些挑战。具有高居里温度（TC）和垂直磁各向异性（PMA）的高质量vdW磁异质结构的可扩展生长工艺将得到发展。该项目将通过利用动量守恒的电子隧道穿越vdW势垒，最大限度地提高MTJs中的隧道自旋极化。利用外延vdW磁异质结构，将演示TMR比高于100%的室温TMR器件的稳健运行。我们有以下雄心勃勃的目标：利用分子束外延技术在TC >= 350 K和PMA条件下可扩展生长高质量的二维磁异质结构。目标2。通过扭转角、偏置和栅极控制，利用动量守恒的电子隧道穿越二维隧道势垒，调节和最大化MTJs中的隧道自旋极化。目标3。利用可扩展外延vdW磁异质结构，展示了TMR比>100%的室温TMR器件的稳健运行。MagicTune将利用外延生长和表征、外延石墨烯模板的合成、隧道磁阻器件、涡旋电子学、量子和自旋输运测量以及全2d纳米器件的纳米制造方面的专业知识。MagicTune的成功将推动TMR器件功能的突破，并使用2D异质结构实现高性能，紧凑和节能的技术。这个项目在多学科纳米科学和纳米技术的前沿有着巨大的前景。

The emergence of atomically thin two-dimensional (2D) materials and their van der Waals (vdW) heterostructures has sparked new scientific interest, offering unprecedented electronic properties for next-generation technologies. 2D magnets, the latest addition to the 2D family, have unique characteristics that make them ideal for vdW heterostructure designs. 2D magnets have the potential to revolutionise magnetic sensors and spintronic technologies, particularly tunnel magnetoresistance (TMR) devices. These devices offer ultra-high sensitivity in magnetic field detection at room temperature, making them invaluable for applications such as magnetic sensors, data storage, memory, and computing. However, reliable and tunable TMR devices pose challenges with conventional materials. Recent advancements have achieved large TMR values using 2D magnets, however most of the reports are limited to cryogenic temperatures and studies are limited to exfoliated flakes. Scalable growth of 2D magnets and the fabrication of magnetic tunnel junctions (MTJs) with multiple layers separated by a tunnel barrier remain challenging and coherent spinpolarised electron tunneling across vdW tunnel barriers on TMR effects is also unexplored. The MagicTune project aims to address these challenges by controlling spin-polarised tunneling in 2D MTJs through twist angle and gate voltage control, achieving large and tunable TMR at room temperature. Scalable growth processes for high-quality vdW magnetic heterostructures with high Curie temperatures (TC) and perpendicular magnetic anisotropy (PMA) will be developed. The project will maximise tunnel spin polarisation in MTJs by exploiting momentum-conserving electron tunneling across vdW barriers. Robust room temperature TMR device operation with TMR ratios above 100% will be demonstrated using epitaxial vdW magnetic heterostructures. We have the following ambitious objectives: Objective 1. Develop scalable growth of high-quality 2D magnetic heterostructures with TC >= 350 K and PMA by molecular beam epitaxy. Objective 2. Tune and maximize the tunnel spin polarization in MTJs by twist angle, bias and gate control by exploiting momentum-conserving electron tunneling across 2D tunnel barriers. Objective 3. Demonstrate robust room temperature TMR device operation with TMR ratio >100% using scalable epitaxial vdW magnetic heterostructures. MagicTune will leverage expertise in epitaxial growth and characterization, synthesis of epitaxial graphene templates, tunnel magnetoresistance devices, twistronics, quantum and spin transport measurements, and nanofabrication of all-2D nanodevices. Success in MagicTune will drive breakthroughs in TMR device functionalities and enable high performance, compact, and energy-efficient technologies using 2D heterostructures. This project holds great promise at the forefront of multidisciplinary nanoscience and nanotechnology.