A cryostat for simultaneous measurements of spontaneous magnetization and AC susceptibility by using a SQUID with a temperature control system was constructed. The temperature of samples can be controlled to an accuracy of 1.2 × 10 -5 at temperatures from 1.6 K to 6.5 K during measurements. This accuracy is obtained by good thermal isolation from their surroundings and use of an isolation amplifier which breaks ground loop currents interfering with the detection of temperature. The SQUID magnetometer consists of a flux locked loop followed by another phase-sensitive detector referenced to the frequency of AC susceptibility. The frequency range of AC susceptibility is from 1 Hz to about 200 Hz and the sensitivity is 2 × 10 -10 emu at 10 Hz with a time constant of 3 seconds, which corresponds to 10 -4 of the flux quantum at a SQUID.
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Ishizuka et al. (1980) studied this question.