Ultrafast magnetic order dynamics in antiferromagnets

在亚皮秒时间尺度上书写全光磁结构的可能性为超快速磁信息存储铺平了道路。关于所使用的材料，纯光诱导开关动力学领域的焦点主要集中在铁磁体上，如GdFeCo，因为已经证明可以用一个持续时间不到100飞秒的单激光脉冲来切换磁化。然而，到目前为止所研究的材料在商业自旋电子器件中的应用有限，这就是为什么寻找其他可用于超快速信息处理的材料的原因。因此，在最后一个申请期间，我们的重点是铁磁体FePt -一种由于其高磁各向异性而已经用于磁性数据存储的材料。通过加入反铁磁耦合元素如Tb、Gd和Cr，研究从低开关铁磁体到超快速开关铁磁体的转变。事实证明，FeCrPt在这方面尤其有希望，并且可以实现极化依赖开关的第一个结果。在我们的更新建议中，我们想把重点转移到反铁磁体上。迄今为止，反铁磁体在自旋电子学中主要是作为纯被动元件与铁磁体结合使用，目前国际上的研究兴趣正在转向主动反铁磁元件。现在已经证明，反铁磁织构可以电写入和读取，作为自旋电子学中反铁磁不可缺少的功能。然而，迄今为止，激光诱导的超快速开关行为仅在有限的范围内进行了研究。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在微观上理解薄反铁磁层（如CrPt或介电氧化物（石榴石，正铁氧体））中的激光诱导开关，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.