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

摘要

We describe a compact capacitive dilatometer for measuring thermal expansion and magnetostriction below 1 K using a home-made capacitance bridge with long-term stability of AC/C ~ 1.6 × 10~(-7). We measured the thermal expansion and magnetostriction of a lieavy-Fermion compound CeRu_2Si_2 and those of a standard copper sample to clarify the dilatometer cell effect. The temperature-dependent cell effect of our dilatometer, ?L/L, was less than 10~(-8) below 0.2 K. The magnetic-field-dependent cell effect was not observed below 52.6 mT at 85 mK, and was less than -2 × 10~(-9) up to 10 T at 4.2 K. Our dilatometer provides precise thermal expansion and magnetostriction measurements at millikelvin temperatures.