Strain sensors based on magnetostrictive GMR/TMR structures

This paper investigates magnetic layer structures suitable for devices measuring mechanical responses such as stress, strain and pressure. Results for giant magnetoresistiance (GMR) multilayers and magnetic tunneling junctions (MTJs) intentionally prepared either with magnetostrictive Fe50Co50 materials or with amorphous Fe-based alloys serving as sensing (or free) layers is discussed in view of possible applications. For MTJs prepared ex-situ with an amorphous FeCoSiB, free layer MR ratios of 33% are obtained leading to gauge factors GF = (DeltaR/R)/Deltaepsilon on the order of 300.