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 Γ_SE=14 000 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.