Phase-locked cantilever magnetometry

摘要

We describe a feedback-based dynamic cantilever magnetometry technique capable of achieving thermal limited magnetic moment sensitivity with low applied fields. Using this technique, we have observed periodic entry of vortices into mesoscopic Sr_2RuO_4 rings. The quantized jump in the magnetic moment of the particle produced by individual vortices was measured with a resolution of 7 X 10~(-16) emu with an applied field of 1 Oe.