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

• Published in: Nature communications Vol. 7; no. 1; p. 12714
• Main Authors: Tao, Y., Eichler, A., Holzherr, T., Degen, C. L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20-09-2016; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1001; 639/925/927; 639/925/930; Disk drives; Hard disks; Humanities and Social Sciences; Measurement techniques; Microscopy; multidisciplinary; Physics; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms12714

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 a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 
μ
B
 Hz
−1/2
, equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole’s strong magnetic gradient of up to 28 × 10
6
 T m
−1
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 ∼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.
The ability to detect weak magnetic moments is important for the study of nanomagnetism and spin-based quantum technologies. Here, the authors demonstrate nanoscale spin detection with high spin sensitivity using a commercial hard drive write head.