Antiferromagnetic spin transport - from Hematite to Orthoferrites

自旋电子学是一个研究领域，主要研究典型的纳米结构材料中的角动量的传输和控制。对于角动量的传输，传统的自旋极化电子被用作金属中的载流子。最近，重点转向使用磁子自旋电流，这种电流可以存在于低阻尼磁绝缘子中，而不会造成欧姆损失。对于这个新兴的绝缘体领域，已经开发了传统的自旋电子学亚铁磁性绝缘体，并且直到最近才证明反铁磁体作为有源组件具有良好的性能，因为反铁磁体的基本功能--电读和写--已经被证明。特别是反铁磁绝缘体，由于其低损耗的自旋输运和超快的动力学特性，最近受到了人们的关注，这预示着它将在下一代自旋电子器件中得到很好的应用。铁锈的主要成分赤铁矿是一种绝缘的反铁磁性矿物，由于其能够远距离传输自旋信息，在这方面是一个很有前途的候选矿物，这一直是我们之前联合项目的重点。在这个后续的计划中，我们希望利用赤铁矿被掺杂的能力来灵活地调节其磁性和输运性质，并特别研究各向异性对自旋输运的影响。除了赤铁矿之外，我们还将研究扩展到一类很有前途的介电反铁磁体，即稀土铁氧体。虽然在磁性方面与赤铁矿有关，但这些材料可以表现出广泛的强各向异性性质，导致自旋重新取向转变、弱铁磁性以及可调阻尼。这个项目将把实验和理论方法结合起来，研究和理解选择性掺杂赤铁矿和特定的正铁氧体中的磁子自旋输运机制。将开发和优化所需的赤铁矿和正铁氧体薄膜的样品生长，同时在从头计算的基础上对自旋模型进行参数化。然后通过磁输运测量、磁成像和多尺度模拟相结合的方法来研究其静磁和动态特性。主要目的是了解组成和掺杂对磁输运的影响。此外，该项目将探索混合准粒子的角动量传输，如磁振子极化子。在了解了传输特性后，我们将最终探索这些材料用于新器件概念的潜力，方法是使用局部门控控制横向传输，并通过磁振子自旋阀控制垂直传输。总而言之，该项目将为当前非常有希望的研究工作奠定基础，以利用反铁磁绝缘体的优势开发新的自旋电子器件。

Spintronics is a field of research that focuses on the transport and control of angular momentum in typically nano-structured materials. For the transport of angular momentum, traditionally spin-polarized electrons have been used as the carrier in metals. More recently, the focus has shifted to using magnonic spin currents, which can exist in low damping magnetic insulators without ohmic losses. For this burgeoning field of insulator spintronics conventionally ferrimagnetic insulators have been developed and only recently antiferromagnets were demonstrated to exhibit favourable properties as active components, since essential functionalities of antiferromagnets - electrical reading and writing - have been demonstrated. Antiferromagnetic insulators, specifically, have recently gained attention due to their low loss spin transport and ultra-fast dynamics boding well for use in next-generation spintronic devices. Hematite, the main constituent of rust, is a type of insulating antiferromagnetic mineral, which is a promising candidate in this context due to its ability to transport spin information over long distances, which has been in the focus of our preceding joint project. Within this follow-up proposal, we want to exploit the ability of Hematite to be doped to flexibly tune its magnetic and transport properties and study in particular the impact of the anisotropy on the spin transport. Beyond hematite, we extend our study to a promising class of dielectric antiferromagnets, which is rare-earth orthoferrites. While related to Hematite in terms of their magnetic properties, these materials can exhibit a wide range of strongly anisotropic properties leading to spin reorientation transitions, weak ferromagnetism, as well as tunable damping. This project will synergetically combine experimental and theoretical approaches to investigate and understand the mechanisms of magnonic spin transport in selectively doped hematite and particular orthoferrites. The necessary sample growth of thin hematite and orthoferrite films will be developed and optimized, while at the same time parameterizing spin models on the basis of ab initio calculations. The magnetostatic and dynamic properties are then investigated by a combination of magneto-transport measurements, magnetic imaging and multiscale simulations. The main goal is the understanding of the effects of the composition and doping on the magnetic transport. Furthermore, the project will probe the transport of angular momentum by hybrid quasiparticles, such as magnon-phonon polarons. Having understood the transport properties, we will finally explore the potential of these materials for use in novel device concepts by controlling lateral transport using local gating and vertical transport across a magnon spin valve. In conclusion, this project will underpin very promising current research efforts to exploit the advantages of antiferromagnetic insulators for the development of new spintronic devices.