BREAKING THROUGH THE 10(-8) EMU SENSITIVITY BARRIER IN MAGNETOMETERS

Traditional SQUID magnetometers offer an ultimate sensitivity of about 5x10(-8) emu and, depending on the system, tile differential sensitiv ity call be as good as 1x10(-8) emu. When magnetometers employ superco nducting solenoids as source of magnetic field, those sensitivities ca n be reduced to values as low as 1x10(-6) emu at fields of 7 Tesla due to magnet ''noise''. Magnet noise is especially a problem under condi tions of continuously ramping applied field, even below 1 Tesla. We ha v deployed a new sample transport mechanism for the Quantum Design SQU ID magnetometer (MPMS), capable of oscillating the sample at frequenci es up to 4 Hz. Using this new technique on measurements of small sampl es, we have demonstrated that differential sensitivities of 3x10(-9) e mu can be achieved. In addition, the new reciprocating sample motion s ignificantly attenuates the magnet noise during measurements.