# Detection of Sub-pT Field of Magnetic Responses in Metals and Magnetic Materials by Highly Sensitive Magnetoresistive Sensors

## TL;DR

A new system detects very weak magnetic responses in materials using a highly sensitive sensor, enabling potential applications in non-destructive testing and medical imaging.

## Contribution

The first reported detection of sub-pT magnetic fields from material responses using a 300 mm spaced sensor and excitation coil setup.

## Key findings

- The system can detect magnetic fields as low as the sub-pT range.
- Signal intensities correlate with the physical mechanisms of magnetic responses.
- The setup maintains a 300 mm distance between the excitation coil and sensor.

## Abstract

We developed a measurement system capable of detecting magnetic responses in various material samples. The system utilizes an excitation coil to apply an alternating magnetic field within the frequency range of 1–10 kHz. The magnetic field generated in the samples was detected using a highly sensitive magnetoresistive sensor. The system demonstrated a detection lower limit in the sub-pT range for magnetic fields arising from magnetic responses such as eddy currents and magnetization changes. The frequency dependence of the detected signal intensities correlated well with the physical mechanisms underlying the magnetic responses. Notably, the distance between the excitation coil and the magnetic sensor was maintained at 300 mm. These results, which demonstrate the detection of a sub-pT magnetic field using a highly sensitive magnetic sensor, have not been previously reported and provide valuable insights for advancing practical applications in non-destructive testing and clinical diagnostic imaging.