Miniature high-sensitivity quartz tuning fork alternating gradient magnetometry

We present a high-sensitivity alternating gradient magnetometer. It uses inexpensive, commercially available, piezoelectric quartz tuning fork resonators as vibration amplitude sensors of a vibrating magnetic sample in an alternating gradient field. The technique exploits the high quality factor, high resonant frequency, and small spring constant of the quartz tuning fork. The instrument also utilizes miniature gradient coils, which allow for large field gradients to be applied to the sample while minimizing the diamagnetic background signal. An instrument noise floor of ${\text{∼1×10}}^{\text{−12}}\hspace{0.17em}\mathrm{emu}/\sqrt{(\mathrm{Hz})}$ has been achieved at room temperature in vacuum. Hysteresis loop measurements on micron sized magnetic samples are demonstrated.