A compact capacitive dilatometer for thermal expansion and magnetostriction measurements at millikelvin temperatures

Abstract

We describe a compact capacitive dilatometer for measuring thermal expansion and magnetostriction below 1K using a home-made capacitance bridge with long-term stability of ΔC/C∼1.6×10−7. We measured the thermal expansion and magnetostriction of a heavy-Fermion compound CeRu2Si2 and those of a standard copper sample to clarify the dilatometer cell effect. The temperature-dependent cell effect of our dilatometer, ΔL/L, was less than 10−8 below 0.2K. The magnetic-field-dependent cell effect was not observed below 52.6mT at 85mK, and was less than −2×10−9 up to 10T at 4.2K. Our dilatometer provides precise thermal expansion and magnetostriction measurements at millikelvin temperatures.