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

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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.