Torque Differential Magnetometry Using the Qplus-Mode of a Quartz Tuning Fork

Quartz tuning fork is the key component of high-resolution atomic force microscope. Because of its high quality factor, quartz tuning fork can also be used for high sensitivity magnetometry. Herein, we developed a highly sensitive torque differential magnetometry using the Qplus-mode of a quartz tuning forks. A sharp resonance of the quartz tuning fork was observed at low temperature down to 25 mK. We calibrated our torque differential magnetometry by measuring the angular dependence of the hysteresis loop in single crystalline Fe_0.25TaS₂. Furthermore, we demonstrated the high sensitivity and the applicability of our torque differential magnetometry in strong magnetic field by measuring the angular dependent quantum oscillations of bismuth single crystal up to 45 T. The extracted Fermi surface cross sections are consistent with previous results. Extra features beyond the quantum limit was also observed, which corresponds to the Landau spectrum at the extreme field limit.