Detection of Low-Frequency Magnetic Fields Down to Sub-pT Resolution with Planar-Hall Effect Sensors

Using planar Hall effect sensors with magnetic flux concentrators, we measure magnetic fields at frequencies below 100 Hz. We show that for a measurement time of up to 100 s, it is possible to detect fields of ~700 fT and ~1 pT at 10 Hz and 0.1 Hz, respectively. In addition, we measure the linearity and hysteresis of the sensor for fields ≤2.6 μT. These features, combined with the sensor miniature size, low power consumption, and potential low cost, may pave the way for usage in a wide range of applications.