Flexible Hall measurement system

霍尔效应在铁磁材料中表现为反常霍尔效应，它与铁磁性薄层的磁化强度的z分量成正比。它可以用来表征磁层系统的磁化状态，甚至可以用来表征磁性微结构。器件的磁化曲线的各种参数可以直接电测得，这是其他技术所不能或仅有的困难。因此，表征具有反常霍尔效应的磁性薄膜系统和器件已成为自旋电子学研究的标准技术。在本提案中，提议为达姆施塔特理工大学的“新材料电子学”工作组购置一套可变霍尔效应测量系统。工作组的工作是用于自旋电子学、反铁磁自旋电子学和自旋轨道扭矩的金属间化合物材料领域。该测量系统的主要组件是一个用于磁场高达2T(磁极间距为20 mm)的水冷电磁铁，一个用于10K至400K之间电测量的定制低温恒温器，以及用于直流和交流锁定测量的测量电子设备。测量系统被故意设计成开放的，以灵活地响应自旋电子学研究的各种要求。例如，该系统将适合于利用反常霍尔效应对磁性薄膜和微结构进行标准表征，也适用于利用平面霍尔测量来研究自旋霍尔效应和自旋霍尔磁阻，以及在可变温度下利用自旋轨道扭矩来探索复杂多层膜系统中磁化强度的电开关。电磁铁的开放式设计还将允许安装激光路径，从而能够使用磁光克尔效应进行磁性表征。因此，这里应用的可变霍尔效应测量系统将成为研究组调查的广泛问题的中心工作工具。

The Hall effect appears in ferromagnetic materials as an anomalous Hall effect, where it is proportional to the z-component of the magnetization of a thin, ferromagnetic layer. It can be used to characterize the magnetization state of a magnetic layer system or even a magnetic microstructure. Various parameters of the magnetization curve of a device can be determined directly electrically, which are not or only with difficulty accessible with other techniques. Therefore, the characterization of magnetic thin film systems and devices with the anomalous Hall effect has become a standard technique in spintronics research. In the present proposal, the acquisition of a variable Hall effect measurement system for the "New Materials Electronics" working group at TU Darmstadt is proposed. The work of the working group is in the area of intermetallic materials for spintronics, antiferromagnetic spintronics and spin-orbit torques. The main components of the measurement system are a water-cooled electromagnet for magnetic fields up to 2T (at 20mm pole spacing), a custom cryostat for electrical measurements between 10K and 400K and measurement electronics for DC and AC lock-in measurements. The measurement system is deliberately designed to be open to respond flexibly to the various requirements of spintronics research. For example, the system will be suitable for using the anomalous Hall effect for standard characterization of magnetic thin films and microstructures, but also for studying the spin Hall effect and spin Hall magnetoresistance using planar Hall measurements, and for exploring the electrical switching of magnetization using the spin-orbit torques in complex multilayer systems at variable temperature. The open design of the electromagnet will also allow the installation of laser beam paths that enable magnetic characterizations using the magneto-optical Kerr effect. Thus, the variable Hall-effect measurement system applied for here will become a central working tool for the wide range of questions investigated by the research group.