High-Sensitivity Atomic Magnetometer Unaffected by Spin-Exchange Relaxation

Abstract

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 $10 f T H z^{- 1 / 2}$ , 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 $2 \times 10^{- 18} T H z^{- 1 / 2}$ .

Received 6 March 2002

DOI:https://doi.org/10.1103/PhysRevLett.89.130801

Authors & Affiliations

J. C. Allred and R. N. Lyman

Department of Physics, Univerisity of Washington, Seattle, Washington 98195

T. W. Kornack and M. V. Romalis^*

Department of Physics, Princeton University, Princeton, New Jersey 08544

^*Author to whom correspondence should be addressed: romalis@princeton.edu

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Physical Review Letters