What is it about?
It is about new applications for the world’s smallest high-precision capacitance dilatometer (height × width × depth = 15 × 14 × 15 mm3, mass: 12 g) and its stress-implementing counterpart. We developed the world’s smallest high-resolution capacitive dilatometer suitable for temperatures from 300 K down to 10 mK and usage in high magnetic fields up to 37.5 T. The new dilatometer with an interchangeable body can also be used for high-resolution measurements of thermal expansion and magnetostriction with and without large stress (up to 3 kbar). We also report two novel applications of both mini-dilatometer cell types. Our new setup was installed for the first time in a cryogen-free system (PPMS DynaCool).
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Why is it important?
Despite the extreme miniaturization, the capacitive dilatometer can resolve length changes down to 0.01 Å. This is an unprecedented resolution in a capacitive dilatometer of this compact size. Many cryogenic devices have limited space. Due to the extremely reduced cell size (height × width × depth = 15 × 14 × 15 mm3, mass: 12 g), implementation or new applications in many of these sample space lacking devices are now possible. As an important example, the minute device can now be rotated in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system (PPMS). One new setup allows the rotation of both dilatometers in situ at any angle between −90○ ≥ μ ≥ +90○ in the temperature range from 320 to 1.8 K. We also installed our mini-cells in a dilution refrigerator insert of a PPMS DynaCool, in which dilatometric measurements are now possible in the temperature range from 4 to 0.06 K. Because of the limited sample space, such measurements could not be performed so far. For both new applications, we can resolve the impressive length changes to 0.01 Å.
Perspectives
Dilatometry, the measurement of the sample length as a function of temperature or magnetic field, is one of the most powerful experimental techniques for the study of strongly correlated electron systems. In particular, the ultrahigh resolution that can be achieved in capacitive dilatometer measurements makes this technique so suitable for studying phase transitions, very low-energy excitations, and the coupling of multiple electronic, orbital, and spin degrees of freedom to the lattice. Compared with other thermodynamic probes such as specific heat, dilatometry has the additional advantage of measuring complementary directional properties such as thermal expansion along different crystallographic directions. Although measurements of the length change can be made using a variety of methods, including X-ray diffraction, optical interferometry, the use of strain gauges, and piezo-cantilever technology, only measurements using the capacitive technique allow for a remarkably high resolution of ΔL/L = 10−10, exceeding the resolution of the other techniques by at least one order of magnitude. Since single crystals of novel materials typically do not exceed 1–3 mm in length, the absolute length change of the sample at low temperatures tends to be extremely small, making the very high resolution of the dilatometer extremely important. Although capacitive dilatometry has been used for decades, it is our miniaturized design that enables the study of complex materials with high resolution and accuracy in challenging environments such as high magnetic fields, at low temperatures and even high uniaxial stress.
Robert Dr. Küchler
Innovative Measurement Technology Kuechler
Read the Original
This page is a summary of: New applications for the world’s smallest high-precision capacitance dilatometer and its stress-implementing counterpart, Review of Scientific Instruments, April 2023, American Institute of Physics,
DOI: 10.1063/5.0141974.
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