Experimental study of topological properties in chiral antiferromagnets

1.我们发现在室温下反铁磁金属Mn_3Sn中存在很大的压磁效应。在某类反铁磁体中，允许应变和磁化之间的线性耦合，并且被称为“压磁”，如果在室温下效果很大，则可以与技术相关。我们发现，通过这种压磁，0.1%的应变可以控制Mn 3Sn中霍尔信号的大小和符号，这是以前在反铁磁体中没有看到的效果。我们与UBC的Dasgupta博士和约翰霍普金斯大学的Tschernyshov教授合作，他们能够构建一个朗道理论，该理论可以在同一框架内解释压磁效应和AHE信号的调制。这项工作已被《自然物理》杂志接受。首次建立了三角形AFM Mn_3Sn的磁性相图。我们成功地生长了Mn 3 + xSn 1-x单晶，范围为0.009 < x < 0.1。我们发现，原始Mn 3Sn的基态是一个无公度的磁序，它是从三角形反手征相分离的一级跃迁在T=280 K。通过磁力和运输测量，我们表明，掺杂锰强烈抑制有利于三角形反手性相的无公度相，但导致在较低温度下出现玻璃状铁磁相。这项工作将是重要的薄膜Mn 3Sn，这是一种材料，最近在自旋电子学社区获得了很大的关注的发展。

1. We found a large piezomagnetic effect in an antiferromagnetic metal Mn3Sn at room temperature. In a certain class of antiferromagnets, a linear coupling between strain and magnetization is allowed and is known as “piezomagnetism”, which can be technologically relevant if the effect is large at room temperature. We found that through this piezomagnetism, a strain in the order of 0.1% can control the magnitude and sign of the Hall signal in Mn3Sn, an effect not previously seen in antiferromagnets. We collaborated with Dr. Dasgupta from UBC and Prof. Tschernyshov from Johns Hopkins University, and they were able to construct a Landau theory which can explain the piezomagnetic effect and the modulation of the AHE signal in the same framework. This work has been accepted into Nature Physics.2. We established the magnetic phase diagram of triangular AFM Mn3Sn as a function of Mn concentration for the first time. We successfully grew Mn3+xSn1-x single crystals within the range 0.009 < x < 0.1. We found that the ground state of a pristine Mn3Sn is an incommensurate magnetic order, which is separated from the triangular antichiral phase by a first-order transition at T=280 K. Through magnetometry and transport measurements, we show that doping Mn strongly suppresses the incommensurate phase in favor of the triangular antichiral phase but leads to the appearance of a glassy ferromagnetic phase at lower temperatures. This work will be important in the development of thin film Mn3Sn, which is a material that has recently gained much attention in the spintronics community.