A miniature capacitance dilatometer for thermal expansion and magnetostriction

A very small capacitive sensor for measuring thermal expansion and magnetostriction of small and irregular shaped samples has been developed. A capacitive method with tilted plates is used. The tilted plate capacitance formula is used for the calculation of the capacitor gap, the calibration is performed by measuring the signal of a standard material. The active length of the sample can be less than 1 mm. The absolute resolution is about 1 A. All mechanical connections of the dilatometer are carried out by tiny Cu-Be springs, enabling the small force on the sample to be adjusted (50-500 mN) and no additional sample fixing is necessary. The cell has been tested in the temperature range 0.3-200 K and in static magnetic fields up to 15 T. The zero signal of the dilatometer has been determined by measuring a silver sample. The correct operation and reproducibility has been verified by measuring the thermal expansion of Cu. The thermal expansion and magnetostriction of a DyCu2 single crystal has been determined. The advantage of this method compared to specific heat measurements is that a large temperature range can be covered with one equipment. This high static and dynamic range of sample length, temperature, and magnetic field suggests a number of possible applications, like the investigation of crystal field effects on the magnetoelastic properties of single crystals or structural phase transitions. (C) 1998 American Institute of Physics. [S0034-6748(98)01007-7].