Fatigue Characteristics of Magnetostrictive Thin-Film Coated Surface Acoustic Wave Devices for Sensing Magnetic Field

Fatigue Characteristics of Magnetostrictive Thin-Film Coated Surface Acoustic Wave Devices for Sensing Magnetic Field

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Magnetostrictive thin-film coated Surface Acoustic Wave (SAW) devices were promising for sensing magnetic field owing to their superior features as micro-size, fast response, and high sensitivity originated from the magnetostrictive effect.However, the magnetostriction nature in magnetostrictive thin-film causes significantly mechanical fatigue in service, deteriorating the sensor performances.In this work, the fatigue phenomenon in magnetostrictive coating was underlined by characterizing the prepared FeCo thin-film coated magnetic device cyclically.

Obvious shedding was observed in FeCo coating after cyclic testing and the magnetic-sensitivity decreases significantly.One of the reasons is nacrack.com the weak adhesion of FeCo thin-film towards the substrate.As an available way allowing enhancement of adhesion, a Cr thin-film was employed as the transition-layer to weaken the mechanical fatigue.

However, it accompanied by the issue of the reduced magnetostrictive coefficient and the obstruction in magnetostrain-tranfer to piezoelectric substrate.As a result, the slump in sensitivity was observed.To address such issues, a design of dotted-pattern with Cr transition layer was employed to build the SAW based magnetic-device.

High magnetic-sensitivity and excellent long-term stability were achieved because of the release of coercive force gtech brush bar in FeCo dots and enhancement of the FeCo adhesion to the substrate.