Liquid-state nuclear spin comagnetometers

We discuss nuclear spin comagnetometers based on ultra-low-eld nuclear magnetic resonance in mixtures of miscible solvents, each rich in a dierent nuclear spin. In one version thereof, Larmor precession of protons and 19F nuclei in a mixture of thermally polarized pentane and hexauorobenzene is monitored via a sensitive alkali-vapor magnetometer. We realize transverse relaxation times in excess of 20 s and suppression of magnetic field fuctuations by a factor of 3400. We estimate it should be possible to achieve single-shot sensitivity of about 5*10^-9 Hz, or about 5*10^-11 Hz in  1 day of integration. In a second version, spin precession of protons and 129Xe nuclei in a mixture of pentane and hyperpolarized liquid xenon is monitored using superconducting quantum interference devices. Application to spin-gravity experiments, electric dipole moment experiments, and sensitive gyroscopes is discussed.