ACCURATE TEMPERATURE REGULATION IN A COMMERCIAL SQUID MAGNETOMETER DURING FAST COOLING

A detailed investigation of tile temperature profile of the measuring region in a commercial SQUID magnetometer was performed over the tempe rature range from approximately 1.75 to 350 K. Temperature measurement s employing three thermometers mounted along the sample tube, revealed the development of a significant thermal gradient during fast cooling from high temperatures. Comparison with measurements of the time depe ndence of the magnetic moment of a Pr2CuO4 single crystal indicated th at long waiting times may be required for sample temperature stabiliza tion depending upon which thermometer is actively used as a control se nsor in the temperature regulation. Highly improved temperature contro l during fast cooling is achieved using a continuous temperature sweep ing mode and a combination of two thermometers.