A new small nano-Kelvin resolution thermometer for low-temperature experiments

A small, high-resolution paramagnetic susceptibility thermometer was developed using a GdCl/sub 3/ paramagnetic salt. The device uses a superconducting quantum interference device (SQUID) magnetometer to determine the temperature dependent magnetization of the salt in a magnetic field. The magnetic field is provided by a pair of small samarium cobalt permanent magnet disks situated inside the thermometer housing. This eliminates the need for a heavy, charging solenoid used in a conventional SQUID-based magnetic thermometer system. This thermometer can resolve approximately 10/sup -9/ K near the liquid-gas critical point of /sup 3/He (/spl sim/3.31 K). The drift rate of the thermometer was measured to be