An Ultrasensitive Differential Capacitive Dilatometer

In this paper, we describe an ultrasensitive differential capacitive dilatometer (ΔL/L ~ 10
^-9
) and novel ratiometric measurement method in the temperature range of 1.9 K <; T <; 400 K for the investigation of thermal expansion and magnetostriction of single crystal as well as polycrystalline samples. The dilatometer provides a capacitive measurement based on a differential capacitance or the capacitance ratio measured between two parallel plate capacitors of the dilatometer. In this regard, an absolute capacitance bridge is not required, and even more advantageously, the effect of adsorbed gas on the capacitor plates is greatly reduced compared to conventional dilatometers. The differential capacitive dilatometer provides a symmetrical configuration which reduces the effect of temperature gradients. The capabilities of the dilatometer are demonstrated by the measurement of magnetic ordering of a URu
₂
Si
₂
sample, and of de Haas-van Alphen oscillations in an aluminum sample.