Improvement of the off-diagonal magnetoimpedance sensor white noise

• A successful approach to sub-pT✓Hz equivalent magnetic noise spectral density was achieved.
• This noise performance is mainly limited by noise level of the electronic conditioning circuitry.
• Irreversible transformation of the magnetic structure of the sensing element occurring with high amplitude excitation has been observed.

This work deals with the analysis of noise sources of the off-diagonal magneto-impedance sensor with stress-annealed amorphous ribbon. This experimental analysis shows that the equivalent magnetic noise spectral density is mostly due to the electronic conditioning circuitry that operates the sensor. The electronic noise was then reduced with employment of an improved excitation-detection technique for our sensor and an equivalent magnetic noise spectral density below 1pT/Hz in white noise region has been reached. Indeed, the equivalent magnetic white noise level of the output signal decreased from 5pT/Hz to 560fT/Hz. Nevertheless, this noise level is still limited by the electronic conditioning, leaving room for further improvement.