Ferrimagnetic Oscillator Magnetometer

Quantum sensors offer unparalleled precision, accuracy, and sensitivity for a variety of measurement applications. We report a compact magnetometer based on a ferrimagnetic sensing element in an oscillator architecture that circumvents challenges common to other quantum sensing approaches such as limited dynamic range, limited bandwidth, and dependence on vacuum, cryogenic, or laser components. The device exhibits a fixed, calibration-free response governed by the electron gyromagnetic ratio. Exchange narrowing in the ferrimagnetic material produces submegahertz transition linewidths despite the high unpaired spin density (approximately 1022 cm-3). The magnetometer achieves a minimum sensitivity of 100 fT/root Hz to ac magnetic fields of unknown phase and a sensitivity below 200 fT/root Hz over a 1 MHz bandwidth. By encoding magnetic field in frequency rather than amplitude, the device provides a dynamic range in excess of 1 mT. The passive, thermal initialization of the sensor's quantum state requires only a magnetic bias field, greatly reducing power requirements compared to laser-initialized quantum sensors. With additional development, this device promises to be a leading candidate for high-performance mag-netometry outside the laboratory, and the oscillator architecture is expected to provide advantages across a wide range of sensing platforms.

Automated summary

Quantum sensors based on a ferrimagnetic sensing element in an oscillator architecture offer a compact and efficient solution for high-performance magnetometry. The device demonstrates a fixed and calibration-free response, with submegahertz transition linewidths and a sensitivity below 200 fT/root Hz over a 1 MHz bandwidth. By encoding magnetic field in frequency, it provides a dynamic range in excess of 1 mT, while its passive thermal initialization greatly reduces power requirements compared to laser-initialized sensors. With further development, this device shows promise for applications outside the laboratory, and the oscillator architecture offers advantages across various sensing platforms.