Cryogen Free Split Pair Magnet Cryostat with Optical Access and Automated Sample Rotation

低温强磁场实验对磁性薄膜和异质结构的研究具有重要意义。此处应用的具有超导分裂对磁体、可变温度插入物和光学通路的干磁体低温恒温器系统应用于研究自旋-热电子输运现象、磁化动力学和磁化阻尼、磁光效应和自旋涨落现象（作为磁场强度、磁场方向和温度的函数）。该系统的一个关键特征是封闭（“干式”）冷却回路，这使得低温液体的再填充变得过时，从而允许在几天甚至几周内进行不间断的高灵敏度测量。该系统的第二个关键特征是能够自动地围绕垂直低温恒温器轴旋转整个样品棒。因此，水平磁场相对于样品的取向可以通过计算机控制远程调节。以这种方式，对于给定的恒定磁场幅度，可以系统地且可再现地记录“角度相关”测量数据（即，作为样本与磁场之间所包围的角度的函数的数据）。样品由此被刚性地安装到可旋转的样品杆上。因此，它可以以最佳方式进行热稳定和电接触-这是计划中的高灵敏度输运和波动实验以及宽带自旋动力学测量的重要先决条件。最后但并非最不重要的是，窗口提供了在平行和垂直于磁场的水平面上对样品的光学访问。除了磁光实验，这使得有可能通过聚焦激光辐射产生局部温度梯度。因此，总体而言，这里应用的磁体低温恒温器系统非常适合我们当前和计划中的研究工作，例如，用于定量研究自旋-热电子现象，如沿沿着不同晶向的交变磁或反铁磁薄膜中的反常霍尔和能斯特效应，测量磁性石榴石或正铁氧体样品中的自旋和磁振子电流，特别是在磁性相变过程中，或研究磁性薄膜和异质结构中的磁化动力学和磁各向异性。

Experiments in large magnetic fields and at low temperatures are of fundamental importance for the investigation of magnetic thin films and heterostructures. The dry magnet cryostat system with superconducting split-pair magnet, variable temperature insert and optical access applied for here shall be used for the investigation of spin-caloritronic transport phenomena, magnetization dynamics and magnetization damping, magneto-optical effects and spin fluctuation phenomena as a function of magnetic field strength, magnetic field direction and temperature. One key feature of the system is the closed (“dry”) cooling circuit, which makes the refilling of cryogenic liquids obsolete and thus allows for uninterrupted, highly sensitive measurements over several days or even weeks. A second key feature of the system is the capability to automatically rotate the entire sample rod around the vertical cryostat axis. Thus, the orientation of the horizontal magnetic field relative to the sample can be adjusted remotely, via computer control. In this way, "angle-dependent" measurement data (i.e. data as a function of the angle enclosed between sample and magnetic field) can be systematically and reproducibly record for a given, constant magnetic field magnitude. The sample hereby is rigidly mounted onto the rotatable sample rod. It can therefore be thermally stabilized and electrically contacted in the best possible way - an important prerequisite for the planned highly sensitive transport and fluctuation experiments, as well as for broadband spin dynamics measurements. Last but not least, windows provide optical access to the sample in the horizontal plane, parallel and perpendicular to the magnetic field. In addition to magneto-optical experiments, this makes it possible to generate local temperature gradients via focused laser radiation. Overall, the magnet cryostat system applied for here therefore is ideally suited for our current and planned research work, e.g., for the quantitative investigation of spin-caloritronic phenomena such as the anomalous Hall and Nernst effect in altermagnetic or antiferromagnetic thin films along different crystal directions, the measurement of spin and magnon currents in magnetic garnet or orthoferrite samples, in particular also across magnetic phase transitions, or the study of magnetization dynamics and magnetic anisotropy in magnetic films and heterostructures.