Phys. Rev. Lett. 89, 130801 (2002) [4 pages]High-Sensitivity Atomic Magnetometer Unaffected by Spin-Exchange RelaxationReceived 6 March 2002; published 9 September 2002 Alkali-metal magnetometers compete with SQUID detectors as the most sensitive magnetic field sensors. Their sensitivity is limited by relaxation due to spin-exchange collisions. We demonstrate a K magnetometer in which spin-exchange relaxation is completely eliminated by operating at high K density and low magnetic field. Direct measurements of the signal-to-noise ratio give a magnetometer sensitivity of 10 fT Hz-1/2, limited by magnetic noise produced by Johnson currents in the magnetic shields. We extend a previous theoretical analysis of spin exchange in low magnetic fields to arbitrary spin polarizations and estimate the shot-noise limit of the magnetometer to be 2×10-18 T Hz-1/2. © 2002 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.89.130801
DOI:
10.1103/PhysRevLett.89.130801
PACS:
07.55.Ge, 32.80.Bx, 33.35.+r
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