Exchange coupling and dipolar interactions in FINEMET/Fe₅₀Pd₅₀ composites ribbons

Asymmetrical giant magnetoimpedance (AGMI) effect was investigated in FINEMET/Fe₅₀Pd₅₀ composite ribbons. Composite ribbon samples of 33 μm-thickness FINEMET sputtered with a layer of Fe₅₀Pd₅₀ film were produced, and the microstructure and magnetic properties were investigated. The results showed that the MI response was enhanced by Fe₅₀Pd₅₀ coating layer. The Fe₅₀Pd₅₀ coating layer generates a bias field to FINEMET ribbon, which leads to the asymmetry of GMI curves. The bias field decreases with the increasing of the thickness (t) of Fe₅₀Pd₅₀ coating layer. The asymmetry of GMI curves almost disappears at t = 70 nm. Asymmetry could be tuned by changing the thickness of Fe₅₀Pd₅₀ coating layer, which is analyzed in terms of exchange coupling and dipole–dipole interaction between FINEMET ribbon and Fe₅₀Pd₅₀ layer. The high sensitivity of GMI was used to separate the two interactions for the first time. The results opened the possibilities for application of FINEMET/Fe₅₀Pd₅₀ composite ribbons in linear magnetic field sensors.