A low field superconducting quantum interference device magnetometer for dynamic measurements

A superconducting quantum interference device magnetometer system designed for low field static and dynamic susceptibility measurements is described. Magnetic shields reduce the residual field in the sample space to about 0.04 A/m (0.5 mOe). A highly stable de magnetic field is generated by a small superconducting solenoid working in the persistent mode. The temperature control system yields a resolution better than 10 mu K in the range of 30-100 K. Combining ac susceptibility and de magnetic relaxation measurements, the system allows dynamic susceptibility studies in a time window ranging from 3 x 10(-6) to 10(6) s. The sensitivity of the system is 10(-12) Am-2 (10(-9) emu). (C) 1997 American Institute of Physics.