Ultrafast magnetic order dynamics in antiferromagnets

在亚皮秒时间尺度上写入全光磁结构的可能性为超高速磁信息存储铺平了道路。关于所使用的材料，纯光感应开关动力学领域的焦点主要是像GdFeCo这样的亚铁磁体，因为已经证明，磁化可以通过持续不到100飞秒的单个激光脉冲来切换。然而，到目前为止，所研究的材料仅用于商业自旋电子器件，这就是为什么继续寻找其他可用于超高速信息处理的材料。在上一个应用阶段，我们的重点是铁磁性FePT-由于其高的磁各向异性，已经被用于磁数据存储的材料。通过添加反铁磁耦合元素，如Tb、Gd和Cr，应该研究从低开关铁磁体到超快开关亚铁磁体的转变。结果表明，FeCrPT在这方面特别有希望，在偏振相关的开关方面可以取得第一个结果。在我们的更新方案中，我们希望将我们的重点转移到反铁磁体上。目前，反铁磁体在自旋电子学中主要作为纯被动元件与铁磁体结合使用，但目前国际上的研究兴趣正在向有源反铁磁元件的方向转移。现在已经证明，反铁磁性织构可以作为自旋电子学中反铁磁体不可或缺的功能来进行电写入和读取。然而，到目前为止，对激光诱导的超快开关行为的研究还很有限。在这个联合项目中，我们希望通过样品制备和表征、激光诱导自旋动力学的光学测量和定量数值模拟方法相结合的方法来研究反铁磁体的超快动力学。我们联合项目的主要目标是微观地理解激光诱导的反铁磁层中的开关，例如CrPT或介电氧化物(石榴石、铁氧体)，研究来自金属顶层的热电子和/或自旋电流对开关行为的影响，以及多尺度模拟，一方面验证模型假设，另一方面有助于理解静态和时间分辨实验。

The possibility of writing all-optically magnetic structures on a sub-picosecond time scale paves the way to ultra-fast magnetic information storage. Regarding the materials used, the focus in the field of purely optically induced switching dynamics was primarily on ferrimagnets such as GdFeCo, since it has already been shown that the magnetization can be switched with a single laser pulse lasting less than 100 femtoseconds. However, the materials investigated so far are only of limited use for commercial spintronic devices, which is why the search for other materials that could be used for ultra-fast information processing continues.In the last application period, our focus was therefore on the ferromagnet FePt - a material that is already used in magnetic data storage due to its high magnetic anisotropy. By adding antiferromagnetically coupling elements such as Tb, Gd, and Cr, the transition from poorly switching ferromagnets to ultra-fast switching ferrimagnets should be investigated. It turned out that FeCrPt in particular is promising in this respect, and first results on polarization-dependent switching could be achieved.In our renewal proposal, we want to shift our focus to antiferromagnets. While antiferromagnets have so far mainly been used as purely passive elements in combination with ferromagnets in spintronics, the interest of international research is currently shifting in the direction of active antiferromagnetic components. It has now been shown that antiferromagnetic textures can be written and read electrically as an indispensable functionality of antiferromagnets for spintronics. However, the laser-induced, ultra-fast switching behavior has so far only been examined to a limited extent. In this joint project we want to investigate the ultrafast dynamics of antiferromagnets through a combination of sample preparation and characterization, optical measurements of the laser-induced spin dynamics and quantitative numerical simulation methods.The main goals of our joint project are the microscopic understanding of laser-induced switching in thin antiferromagnetic layers such as CrPt or dielectric oxides (garnets, orthoferrites), the investigation of the influence of hot electrons and/or spin currents from a metallic top layer on the switching behavior, and multiscale simulations, on the one hand to verify the model assumptions and on the other hand to contribute to the understanding of the static and time-resolved experiments.