The limits of detection for superconducting quantum interference devices (SQUID), optical pumped magnetometer (OPM), Fluxgate, and magneto-impedance (MI) sensors at 10 Hz are approximately 1 fT/ √ Hz [1], 10 fT/ √ Hz [2], 5 pT/ √ Hz [3], and 10 pT/ √ Hz [4], respectively.