Paramagnetic Cooling

Abstract

We have constructed an adiabatic demagnetization cryostat with a non-ferromagnetic stainless steel chamber. A singlecrystal synthetic ruby was used as the paramagnetic salt. The final-temperature dependence on the applied magnetic field, generated by a superconducting magnet, was investigated. The results obtained agree fairly well with an extremely simple theoretical calculation within the limits of the theory. Temperatures below 1°K were measured by a susceptibility thermometer using the a-c method. Superconductive tunnel junctions were evaporated onto the flat end of the ruby crystal and attempts were made to observe the properties of these junctions at low temperatures using the ruby as a coolant. Difficulties involved and suggestions on improvements for future thin-film experiments have been discussed.