Evaluation of Directional Dependence of Sensitivity for Room-Temperature Magnetic Flux Sensors With Wide Sensitivity Region

Recently, the room-temperature (RT) magnetic flux sensors have begun to be applied to biomagnetic measurements. The RT sensors have a large advantage that they can be placed closer to the magnetic sources and obtain larger signals, unlike the superconducting quantum interference device (SQUID) flux sensors. However, when an RT sensor is placed closer to the sources, the dimension of the sensitivity region cannot be negligible, and the directional dependence of sensitivity should be considered to estimate the theoretical magnetic signals for magnetic source analysis. We proposed a method to evaluate the directional dependence of the sensitivity of the RT sensors in response to adjacent magnetic sources using the array of coils arranged along a circular arc. Consequently, it was revealed that a specific magnetoresistance device-based flux sensor with a certain spatial extent had the directional dependence of sensitivity with a bell-shaped profile. We also proposed the multiple sensitivity points model for the bell-shaped profile and estimated the sensitivity distribution over the sensitivity region, which is expected to be effective in improving the accuracy of the magnetic source analysis using an RT sensor array.