Trilayer GMI sensors based on fast stress-annealing of FeSiBCuNb ribbons

Magneto-elastic properties and creep-induced anisotropy dependence of giant magneto-impedance (GMI) behaviour in nanocrystalline Fe75Si15B6Cu1Nb3/Cu/Fe75Si15B6Cu1Nb3 sandwich structures are reported. Magnetic ribbons are submitted to stress (5–175 MPa) and rapid annealing (a few tens of a second) at temperatures between 500 and 800 °C. In contrast with amorphous systems, transfer curves of nanocrystalline GMI sensors can be easily controlled by creep-induced anisotropy. High values of GMI ratio (a few hundreds of percent) are obtained in the radio frequency range. Nanotesla range is detectable with a sensitivity of 4500 V/A/T up to 1 kHz. These performances are interesting for magnetic sensors in non-destructive testing of embedded cracks, ac/dc space magnetometers, molecular recognition systems and selective detection applications.