Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head

TL;DR

This paper demonstrates that a commercial hard drive write head can be used as an ultrasensitive nanoscale magnetic sensor, achieving high spin sensitivity and spatial resolution for applications in condensed matter physics.

Contribution

The study introduces a novel use of commercial disk drive write heads for ultrasensitive magnetic detection at the nanoscale, combining mechanical force sensing with magnetic field imaging.

Findings

Achieved a spin sensitivity of 0.032 Bohr magnetons per root Hz.

Demonstrated magnetic field imaging with 10 nm spatial resolution.

Utilized the high magnetic gradient of the write head for enhanced sensitivity.

Abstract

Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins, and nanoscale magnetic resonance imaging. Here, we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from the pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 Bohr magnetons per root Hz, equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 million Tesla per meter and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with about 10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation, and mesoscopic physics.