Cryogen-free 14 T cryostat system for magnetic, thermal and electrical characterization

• Subject Area: Condensed Matter Physics
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 570052800

The proposed large-scale device consists of a cryogen-free, top-loading cryostat system, which permits a temperature range of 1.8 K to 1000 K as well as the application of a homogeneous magnetic field of ±14 T at the sample position for magnetometry measurements. It’s designed as a modular system and can be used for a wide variety of measurement types by changeable inserts (options), also enabling the use of self-built setups. For our use case, it’s decisive for the device to be equipped with a vibrating sample magnetometer (VSM) option, which allows the comprehensive characterization of magnetic properties (such as magnetic moment) of e.g. thin film and powder samples in a high maximum field of 14 T. The 9 T maximum field of the current devices, as well as the limited measurement time available, are not sufficient for the detailed analysis of complex sample systems. Our project lead in three collaborative research centres (CRCs), several standalone projects and cooperation networks, cause an urgent demand for high-precision magnetic characterization of a large number of samples, such as in the comparative study of the CRC/TRR 247 “Heterogeneous Oxidation Catalysis in the Liquid Phase”. This CRC gives rise to a strong demand for measurements at magnetic fields above 9 T, in order to bring the increasingly cobalt-rich spinels with their partially antiferromagnetic ordering into a state of saturation via the application of up to 14 T. The CRC/TRR 270 “Hysteresis Design of Magnetic Materials for Efficient Energy Conversion” deals with the behavior of application-oriented magnetic functional materials. Our measurements are pivotal for this research in the CRC/TRR 270, in which magnetic cooling is one of the key points. For this purpose, we propose the acquisition of the heat capacity measurement option, as it’s a decisive parameter for the optimization of magnetocaloric materials systems. By means of the AC-susceptometry option, the proposed device is slated to replace our 30-year-old SQUID magnetometer, as its high helium consumption is at odds with current-day standards of sustainability. Extensive AC-measurements were conducted in the currently running DFG-project “Orientierungsphänomene in magnetischen Flüssigkristall-Hybridmaterialien” to characterize dynamic effects in ferrofluids and -gels. A modification of the device further enables measurements of the converse magnetoelectric effect, where we build upon our results and experience from the research group FOR 1509 “Experimental characterization of magneto-electric composites”.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Kryogenfreies 14 T Kryostatsystem zur magnetischen, thermischen und elektrischen Charakterisierung
• Instrumentation Group: 8550 Spezielle Kryostaten (für tiefste Temperaturen)
• Applicant Institution: Universität Duisburg-Essen
• Leader: Professor Dr. Heiko Wende