Abstract
A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency under conditions where its intrinsic spin dominates over its rotational angular momentum, ( is the moment of inertia of the needle about the precession axis and is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time of the quantum- and detection-limited magnetometric sensitivity is . The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics.
- Received 8 February 2016
DOI:https://doi.org/10.1103/PhysRevLett.116.190801
© 2016 American Physical Society
Physics Subject Headings (PhySH)
Focus
Supersensitive Needle Magnetometer
Published 13 May 2016
A tiny, needle-shaped ferromagnet could form a magnetic sensor far better than the current best instruments, according to theory.
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