Simple microcalorimeter for measuring microgram samples at low temperatures

An innovative microcalorimeter has been developed for measuring specific he at of very small microgram samples in the temperature range from 1.5 to 50 K and in magnetic fields up to 11 T. The device is built from a commercial sapphire temperature chip (Cernox), which is modified by means of standard microfabrication techniques and which is used as a sample holder, temperatu re sensor, and sample heater. Compared to existing microcalorimeters the si mple design of our instrument allows a fabrication of the device in a few p rocess steps by using facilities present in a standard laboratory clean roo m. As an illustrative example for the performance of our device, the specif ic heat of an underdoped (La1-xSrx)(2)CuO4 and CaRuO3 single crystal has be en measured by means of the relaxation time method as well as the ac method . (C) 2001 American Institute of Physics.