Spin-exchange-relaxation-free magnetometry with Cs vapor

We describe a Cs atomic magnetometer operating in the spin-exchange- relaxation-free (SERF) regime. With a vapor cell temperature of 103°C we achieve intrinsic magnetic resonance widths ΔB=17 μG corresponding to an electron spin-relaxation rate of 300 s-1 when the spin-exchange rate is ΓSE =14000 s-1. We also observe an interesting narrowing effect due to diffusion. Signal-to-noise measurements yield a sensitivity of about 400 pG/ Hz. Based on photon shot noise, we project a sensitivity of 40 pG/ Hz. A theoretical optimization of the magnetometer indicates sensitivities on the order of 2 pG/ Hz should be achievable in a 1 cm3 volume. Because Cs has a higher saturated vapor pressure than other alkali metals, SERF magnetometers using Cs atoms are particularly attractive in applications requiring lower temperatures.