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Liquid-free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature and solid-state physics to graduate students and specialists. Most of the devices are relatively expensive, but small-sized equipment is slowly becoming available. Here, we have designed several simple experiments which can be performed using a small Stirling refrigerator. We discuss the measurement of the critical current and temperature of a bulk YBa[subscript 2]Cu[subscript 3]O[subscript 7 - [delta]] (YBCO) sample, the observation of the levitation of a magnet over a YBCO disc when cooled below the critical temperature and the observation of a phase transition using ac calorimetry. The equipment can be easily handled by students and also used to teach the principles of liquid-free cooling. (Contains 10 figures and 8 footnotes.)

Liquid-free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature and solid-state physics to graduate students and specialists. Most of the devices are relatively expensive, but small-sized equipment is slowly becoming available. Here, we have designed several simple experiments which can be performed using a small Stirling refrigerator. We discuss the measurement of the critical current and temperature of a bulk YBa2Cu3O7-d (YBCO) sample, the observation of the levitation of a magnet over a YBCO disc when cooled below the critical temperature and the observation of a phase transition using ac calorimetry. The equipment can be easily handled by students and also used to teach the principles of liquid-free cooling. [ABSTRACT FROM AUTHOR]

We present thermoelectric power and resistivity measurements in the ferromagnet UGe2 as a function of temperature and magnetic field. At low temperature, huge quantum oscillations are observed in the thermoelectric power as a function of the magnetic field applied along the a axis. The frequencies of the extreme orbits are determined and an analysis of the cyclotron masses is performed following different theoretical approaches for quantum oscillations detected in the thermoelectric power. They are compared to those obtained by Shubnikov-de Haas experiments on the same crystal and previous de Haas-van Alphen experiments. The agreement of the different probes confirms thermoelectric power as an excellent probe to extract simultaneously both microscopic and macroscopic information on the Fermi surface properties. Band structure calculations of UGe2 in the ferromagnetic state are compared to the experiment. [ABSTRACT FROM AUTHOR]