Breaking through the 10−8 emu sensitivity barrier in magnetometers
Traditional SQUID magnetometers offer an ultimate sensitivity of about 5×10−8 emu and depending on the system, the differential sensitivity can be as good as 1×10−8 emu. When magnetometers employ superconducting solenoids as source of magnetic field, those sensitivities can be reduced to values as low as 1×10−6 emu at fields of 7 Tesla due to magnet “noise”. Magnet noise is especially a problem under conditions of continuously ramping applied field, even below 1 Tesla. We have deployed a new sample transport mechanism for the Quantum Design SQUID magnetometer (MPMS), capable of oscillating the sample at frequencies up to 4 Hz. Using this new technique on measurements of small samples, we have demonstrated that differential sensitivities of 3×10−9 emu can be achieved. In addition, the new reciprocating sample motion significantly attenuates the magnet noise during measurements.
