How do we work?
| "Aright, nobody move! I've got a dragon and I'm not afraid to use it!" ["Shrek", the movie] |
Specific heat measurements
by Adam Pikul
The most important experimental method in our studies of strong electronic correlations in f-electron systems are heat-capacity measurements. The Quantum Design Physical Property Measurement System is nowadays the only commercially available apparatus, which allows to measure specific heat of small solid samples in a wide temperature range, with high accuracy, fully automatically and using only one experimental setup.
The sample of a mass of the order of a few milligrams is glued to a high-purity
sapphire plate, which has at the lowest temperatures extremely small value of the
absolute heat capacity (of the order of a few nanojoules per kelvin!). That plate,
together with a heater and a thermometer, serves as a sample platform, which holds the sample,
heats it with some power ΔQ, and measures an increase of its temperature ΔT.
The heat capacity of the sample can be basically calculated as C=ΔQ/ΔT.
High absolute sensitivity of that apparatus (up to about 1 × 10-9 J/K
at 330 mK) is achieved thanks to the utilization of thermal relaxation method,
which is one of the most sensitive technique in microcalorimetry.
High capacity liquid helium dewar with liquid nitrogen jacket allows to reach 4.2 K in the experimental chamber. By lowering the vapor pressure of the liquid helium one can get even 1.9 K. The optional 3He-fridge moves that limit down to 330 mK. Thanks to a build-in heater the upper limit of the experiments is 400 K. All the experiments can be performed in steady external magnetic fields up to 9 T, generated by a standard superconducting NbTi-magnet.
Summary
- Experiment: specific heat as as a function of temperature in steady magnetic fields
- Temperature range: 1.9 - 400 K (down to 330 mK using the optional 3He fridge)
- Magnetic field range: 0 - 9 T
- Technique: thermal relaxation method
- Absolute sensitivity: up to 1 nJ/K
- Typical sample mass: 1-10 mg (up to 150mg)
- Typical sample size: 1 x 1 x 0.5 mm3
