Keder, David A.Prescott, David W.Conovaloff, Adam W.Sauer, Karen L.2015-09-102015-09-102014-12-31Keder, David A., David W. Prescott, Adam W. Conovaloff, and Karen L. Sauer. “An Unshielded Radio-Frequency Atomic Magnetometer with Sub-femtoTesla Sensitivity.” AIP Advances 4, no. 12 (December 1, 2014): 127159. doi:10.1063/1.4905449.https://hdl.handle.net/1920/9830We demonstrate a radio-frequency potassium-vapor magnetometer operating with sensitivities of 0.3 fT/√Hz at 0.5 MHz and 0.9 fT/ √Hz at 1.31 MHz in the absence of radio-frequency and mu-metal or magnetic shielding. The use of spatially separated magnetometers, two voxels within the same cell, permits for the subtraction of common mode noise and the retention of a gradient signal, as from a local source. At 0.5 MHz the common mode noise was white and measured to be 3.4 fT/ √Hz; upon subtraction the noise returned to the values observed when the magnetometer was shielded. At 1.31 MHz, the common mode noise was from a nearby radio station and was reduced by a factor of 33 upon subtraction, limited only by the radio signal picked up by receiver electronics. Potential applications include in-the-field low-field magnetic resonance, such as the use of nuclear quadrupole resonance for the detection of explosives.en-USAttribution 3.0 United StatesCalibrationEnvironmental noiseMagnetic resonanceStatic magnetic fieldsCoilsArticlehttp://dx.doi.org/10.1063/1.4905449