Magnet and Low Temperature Facility
Technological Institute, FB24
TEL: (847) 491-4212
Facility Director: John B. Ketterson, (j-ketterson@northwestern.edu) Physics & Astronomy Department
Facility Technician: Oleksandr Chernyashevskyy (o-chernyashevskyy@northwestern.edu)
FUNCTION:
This facility maintains various magnet and cryogenic systems operating either separately or together. The systems are designed to be as flexible as possible, and to allow several types of measurements to be performed over a wide range in magnetic field, temperature, and probe frequency. The types of measurements that are routinely performed include magnetization and magnetic susceptibility, acoustic propagation, microwave absorption, and electrical transport (including thermoelectric measurements).
EQUIPMENT:
Our equipment includes cryostats, magnets, magnetometers, a nanovoltmeter, constant-current sources, and constant-voltage sources. The magnetometers include a computer-controlled Quantum Design Magnetometer (MPMS5) that permits SQUID magnetic-moment sensitivity (and a user probe for transport measurements), a LAKESHORE AC susceptometer for measuring both real and imaginary components of susceptibility, and a quick-turnaround AC bridge susceptometer. The MPMS provides the exceptional sensitivity of a SQUID-based magnetometer in a fully automated, analytical instrument. It provides a much needed solution for a unique class of magnetic measurements, meeting the needs of research in key areas such as high-temperature superconductivity, biochemistry, and magnetic recording media. This system was upgraded in 2004 by the addition of a horizontal rotator option and an "oven" insert for high-temperature measurements. This instrument can measure DC magnetic susceptibility and magnetic moments on samples as small as a few mg.
Field range: -5.0 T to 5.0 T Temperature range: 1.8 K to 700 K Measurement range: 10 -7 to 100 emu Absolute sensitivity: 10 -7 emu Additional cryostats include a computer-controlled Quantum Design Physical Properties Measurement System (PPMS) and a SHE VTS 50 SQUID susceptometer outfitted for low-noise transport measurements. The PPMS was designed to measure heat capacity, thermal transport, and thermoelectric effects. Key optional features of the MPMS have been greatly expanded and improved in the PPMS. The PPMS brings a new level of measurement automation to researchers in rapidly expanding fields such as materials science, condensed matter physics, biology and analytical chemistry. The tremendous flexibility of the PPMS - open architecture - lets you create your own experiments and easily interface your own third-party instruments to the PPMS hardware. For example, we can connect a user's equipment to PPMS analog outputs with signals proportional to magnetic field, system temperature, bridge resistance, bridge excitation, etc.
Field range: -9.0 T to 9.0 T
Temperature range: 1.9 K to 390 K
Thermal conductance accuracy: 5%
Heat capacity sample size: 1 to 200 mg
Heat capacity resolution: 10nj/K at 2 K
Ease Of Use The hallmarks of our instruments are automation and ease of use. We can quickly and easily configure them to perform different types of measurements. In a matter of minutes we can install a measurement application, set up an automated sequence, and start collecting meaningful data. And, our equipment is designed to run 24 hours a day, 7 days a week. We know your time is valuable, so we have laboratory automation on a new level. While the PPMS or MPMS runs your measurements, you can be analyzing data from previous measurements, planning your next experiment, and creating new materials. The MPMS and PPMS work like dedicated systems, but their tremendous flexibility lets you perform different types of measurements. Plus, we can easily integrate a user's unique experiment with our measurement systems. Samples can be easily prepared from a variety of materials. The exceptional dynamic range of our devices allows us to accommodate samples in many forms, from single crystals to bulk solids, films and powders.
Selected Recent Publications
I. P. Nevirkovets, O. Chernyashevskyy, J. B. Ketterson, and E. Goldobin, Fabrication and characterization of multi-terminal superconductor - insulator - normal metal - insulator - superconductor Josephson devices. J. Appl. Phys. 97, 123903 (2005).
I. P. Nevirkovets, O. Chernyashevskyy, and J. B. Ketterson, Direct study of the proximity effect in the normal layer inside of the stacked SINIS device. Phys. Rev. Lett. 95, 247008 (2005).
I. P. Nevirkovets, O. Chernyashevskyy, and J. B. Ketterson, Characteristics of Zr-based single- and multiple-barrier superconducting tunnel junctions, Appl. Phys. Lett. 88, 212504 (2006).
I. P. Nevirkovets, O. Chernyashevskyy, and J. B. Ketterson, Absence of enhanced superconductivity in double-barrier superconducting tunnel junctions: Measurements of lateral electric transport in the middle normal-metal layer, Phys. Rev. B 73, 224521 (2006).
I. P. Nevirkovets, O. Chernyashevskyy, and J. B. Ketterson, Direct Observation Of The Proximity Effect In The N Layer In A Multi-Terminal SINIS Josephson Junction. AIP Conf. Proc. 850, 983-984 (2006). (Proceedings of LT24).
I. P. Nevirkovets, S. E. Shafranjuk, O. Chernyashevskyy, and J. B. Ketterson, Enhancement of the supercurrent at a finite voltage in a sandwich-type ballistic SINIS junction. Phys. Rev. Lett. 98, 127002 (2007).
I. P. Nevirkovets, S. E. Shafranjuk, O. Chernyashevskyy, and J. B. Ketterson, Enhancement of the Josephson critical current in a multiterminal SINIS device under current injection. Phys. Rev. B 76, 184520 (2007).