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

在大磁场和低温下的实验对于磁性薄膜和异质结构的研究是非常重要的。本文所采用的超导分裂磁体、变温插入器和光学通路的干磁体低温恒温器系统将用于研究自旋-热电子输运现象、磁化动力学和磁化衰减、磁光效应和自旋涨落现象随磁场强度、磁场方向和温度的变化。该系统的一个主要特点是封闭式(“干式”)冷却回路，这使得低温液体的再灌装变得过时，从而允许在几天甚至几周内进行不间断、高灵敏度的测量。该系统的第二个关键特征是能够自动围绕垂直低温恒温轴旋转整个样品棒。因此，水平磁场相对于样品的方向可以通过计算机控制进行远程调整。这样，对于给定的恒定磁场大小，可以系统地和可重现地记录与角度相关的测量数据(即，作为样品和磁场之间夹角的函数的数据)。在此，样品刚性地安装在可旋转的样品棒上。因此，它可以以尽可能好的方式进行热稳定和电接触--这是计划中的高灵敏度输运和涨落实验以及宽带自旋动力学测量的重要前提。最后但并非最不重要的一点是，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，这使得通过聚焦激光辐射产生局部温度梯度成为可能。因此，总的来说，这里应用的磁控低温系统非常适合我们目前和计划进行的研究工作，例如用于定量研究自旋量热现象，如沿不同晶体方向的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，尤其是跨磁相变，或者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.