Strain sensitivity of highly magnetostrictive amorphous films for use in microstrain sensors

Strain sensitivity of amorphous (Fe90Co10)78Si12B10 sputtered film was studied in detail, so as to examine the potential of film for highly sensitive microstrain gauges. The film exhibited the figure of merit F=(Δμ/μ)/ε (change in film permeability μ per unit strain ε) of 1.2×105, the value of which is comparable to that of amorphous ribbons. Reflecting the large value of F, the high-frequency impedance of the film was also subjected to change due to strain: the change in impedance of 46% was observed at 100 MHz applying a strain of 300×10−6. It is also demonstrated that utilizing the strain-dependent impedance, a small strain of 0.2×10−6 can be detected with the film.