Overhauser proton spin-echo magnetometer for magnetic fields below 1 ${ m mu}$ T

Overhauser dynamic nuclear polarization (O-DNP) can significantly boost the intensity of the nuclear magnetic resonance (NMR) signal in comparison to the thermal magnetization for field strengths in the microtesla range. We demonstrate the development and use of an Overhauser spin-echo magnetometer using a superconducting quantum interference device-based microtesla NMR system and dissolved nitroxide radicals in deoxygenated tetramethylsilane liquid. A spin-echo train with an enhanced signal was successfully obtained with the O-DNP technique. A magnetic field strength of about 0.92 mu T was measured with an uncertainty of 0.7 pT in the presence of a field gradient of 0.038 mu T cm(-1). The Overhauser proton spin-echo magnetometer will be useful for the measurement of low magnetic fields by minimizing the generation of disturbing magnetic fields without the need to compensate for residual field gradients.