  We report an optical inelastic-wave-mixing-enhanced atomic magnetometry
technique that results in nT-level magnetic field detection at temperatures
compatible with the human body without magnetic shielding, zero-field
compensation, or high-frequency modulated phase-locking spectroscopy. Using
Gaussian magnetic pulses that mimic the transient magnetic field produced by an
action potential on a frog's nerve, we demonstrate more than 300,000-fold
(550-fold) enhancement of magneto-optical rotation signal power
spectral-density (power amplitude) over the conventional single-beam
$\Lambda-$scheme atomic magnetometry method. This new technique may bring
possibilities for extremely sensitive magnetic field imaging of biological
systems accessible via an optical fiber in clinical environments.
