TECHNICAL DESCRIPTION

This technology involves a method for obtaining a nanocrystalline material with magnetic characteristics from the FINEMET family (Fe, Si, B, Cu, Nb): relative magnetic permeability higher than 10 000,  great thermal stability, non magnetostrictive, low hysteresis (its remanence is lower than 0.02T).
Then, the invention describes how to manufacture a new device of magnetic field detection using giant magneto-impedance effect based on the element mentioned previously. The device is composed, on a side by the sensor itself which is the interposition of a conducting layer between two layers of magnetic material, and on another side by the electronic circuit associated.
The dimensions of the sensor are important for optimizing the measures abilities of the device which reaches a high impedance variation (around 1000%), a high sensitivity to fields (5-10%/A/m) and have a space resolution from 10µm to 1mm.
One type of measure is the detection of impedance variation according to external magnetic field when an AC current of amplitude of 10mA and frequency 10KHz-2MHz is passing through the sensor. Another technique is to measure the voltage induced at the ends of a pick-up coil surrounding the sensing element.

INDUSTRIAL APPLICATION

The applications of this invention, which allow to have a system smaller but more precise than the previous sensors, are very numerous and the principal one is the non destructive testing based on the use of eddy currents for aerospace, nuclear, micro-electronics and car industry.
This very sensitive magnetic sensor can also be embedded in RFID features or as a measure device in biochips for locating the magnetic markers (nanoparticles). The monitoring of current in integrated power devices and magnetic sensors in data storage applications are also other possible markets for this kind of sensor.