The Physics/Astronomy Department has two SQUID susceptometers from Quantum Design, Inc. Both systems have the capability of making fast, precise measurements of the cd magnetic properties of materials over a wide range of temperature and applied fields. They are capable of resolving variations in magnetic moment as small as 10-8 emu.
One of the systems has the capability of measuring the ac susceptibility over a wide range of frequencies and ac magnetic fields. Measurements that use only a dc magnetic field provide no information about dissipative mechanisms in the sample. However, by applying an oscillating magnetic field to the sample, the induced magnetic moment will exhibit dissipative mechanisms. Thus the measurement provides us with both real (in-phase) and imaginary (out-of-phase) components of the magnetic susceptibility, where the imaginary part is proportional to the energy dissipation in the sample.
The ac SQUID also has a Low Field capability which allows the user to achieve very low residual fields. An Environmental Magnetic Shield is added, which provides attenuation of external magnetic fields. The ac measuring field can be varied from 0.0001 to 5.94 Gauss with a frequency of range of 0.00035 to 1512 Hz, while the High Field SQUID system provides temperatures from 2 to 400 K and fields up to 5.5 Tesla, the ac one covers the temperature range 2 to 350 K with magnetic fields up to 1 Tesla.
For information regarding using the SQUID, contact Dr. Reza Loloee.