Materials World Network: Ultrafast All-Optical Switching in Ferri-/Ferromagnetic Nanomagnets

纳米磁体被考虑用于下一代数据存储介质和其他自旋电子学应用已经有一段时间了。近年来，亚铁磁性材料中磁取向的超快全光开关的发现引起了人们的极大兴趣。这种光开关层与交换耦合的铁磁存储层的潜在组合非常耐人寻味，并提出了许多令人兴奋的材料问题。本项目将在具有超短开关时间的纳米存储介质的背景下，系统地探索FeTb-FePtCu异质结构。Holger Schmidt的应用光学小组(美国加州大学圣克鲁斯分校)和Manfred Albrecht的磁性纳米结构小组合作的目标是结合我们在图案化纳米磁材料制备和表征方面的独特能力，来研究与这种新型材料系统相关的一些问题：(A)我们将首次展示使用铁磁性材料(这里是FeTb)的单畴纳米磁网中的全光磁化开关。我们将研究这一效应与FeTb中补偿点温度的依赖关系。(B)我们将首次制备交换耦合的FeTb-FePtCu异质结。FePtCu具有可调的磁各向异性、居里温度和结晶学特性，是一种极具吸引力的磁存储材料。我们将确定FePtCu层的静态磁性能对与FeTb的交换耦合的依赖性。(C)我们将演示通过来自全光控制的FeTb层的交换耦合来实现单个FePtCu纳米磁体的超快开关，从而将亚铁磁体中的高速开关与铁磁层的硬磁存储能力相结合。(D)我们将研究全光开关对两个外部参数的依赖性：(1)通过比较弯曲纳米磁体与相同尺寸的平板磁体的三维形状，以及(2)使用近场时间分辨磁光检测的密集阵列中的磁环境。这项研究只有通过结合Albrecht集团的材料专业知识和Schmidt集团开发的单个纳米磁铁检测能力才能实现。

Nanomagnets have been under consideration for next generation data storage media and other spintronics applications for some time. Recently, the discovery of ultrafast all-optical switching of magnetic orientation in ferrimagnetic materials has received a lot of interest. The potential combination of such an optical switching layer with an exchange-coupled ferromagnetic storage layer is highly intriguing and raises a number of exciting material questions. This project will systematically explore FeTb-FePtCu heterostructures in the context of nanoscale storage media with ultrashort switching times. The goal of this collaborative effort between the Applied Optics group of Holger Schmidt (UC Santa Cruz, USA) and the Magnetic Nanostructures group of Manfred Albrecht (Chemnitz University of Technology, Germany) is to combine our unique capabilities for fabrication and characterization of patterned nanomagnetic materials to investigate a number of questions related to this novel material system:(a) We will for the first time demonstrate all-optical magnetization switching in single-domain nanomagnets using ferrimagnetic materials, here FeTb. We will investigate the dependence of this effect on the composition-dependent compensation point temperature in FeTb.(b) We will, for the first time, fabricate exchange-coupled FeTb-FePtCu heterostructures. FePtCu is attractive as magnetic storage material with adjustable magnetic anisotropy, Curie temperature, and crystallography. We will determine the dependence of the static magnetic properties of the FePtCu layers on the exchange coupling with FeTb.(c) We will demonstrate ultrafast switching of single FePtCu nanomagnets via exchange coupling from an all-optically controlled FeTb layer, thus combining the high-speed switching in a ferrimagnet with the hard magnetic storage capabilities of a ferromagnetic layer.(d) We will investigate the dependence of all-optical switching on two external parameters: (1) the three-dimensional shape of the nanomagnets by comparing curved nanomagnets with flat counterparts of the same size, and (2) the magnetic environment in a dense array using time resolved magneto-optic detection in the near field.This research is only enabled through the combination of the materials expertise of the Albrecht group and the single nanomagnet detection capabilities developed in the Schmidt group.