title: 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 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 2x10(-18) T Hz(-1/2).
authors.affiliation: Department of Physics, Univerisity of Washington, Seattle, Washington 98195, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Allred
authors.forename: R N
authors.initials: RN
authors.lastname: Lyman
authors.forename: T W
authors.initials: TW
authors.lastname: Kornack
authors.forename: M V
authors.initials: MV
authors.lastname: Romalis
mesh_terms: D008280:Magnetics / Q000295:instrumentation; D008962:Models, Theoretical; D011188:Potassium / Q000737:chemistry
chemical_list: D011188:Potassium