Optically pumped atomic magnetometers are fundamentally limited by spin-exchange relaxation in finite magnetic fields. In conventional parametric resonance magnetometers (PRMs), this relaxation dominates the resonance linewidth, producing broad profiles that degrade sensitivity. Here, we suppress this relaxation by incorporating light narrowing via optical pumping into spin-stretched states in a longitudinally modulated PRM, which directly enables dual-axis vector detection of transverse magnetic fields through lock-in demodulation. Under optimized conditions, the magnetometer achieves transverse sensitivities of $210\mathrm{fT}/\sqrt{\mathrm{Hz}}$ and $290\mathrm{fT}/\sqrt{\mathrm{Hz}}$ along two orthogonal axes, a 3-dB bandwidth of about $500\mathrm{Hz}$, and excellent cross-axis discrimination—an order-of-magnitude improvement over conventional PRMs. This work demonstrates that light narrowing effectively overcomes the spin-exchange limitation in finite-field operation, providing a promising route for high-sensitivity vector magnetometry in applications such as atomic gyroscopes and active magnetic compensation.

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• Atomic & molecular processes in external fields
• Optical pumping