Exchange coupling and dipolar interactions in FINEMET/Fe50Pd50 composites ribbons

•As the thickness of Fe50Pd50 coating layer increases, the dominance of exchange coupling and dipole–dipole interaction could be clearly separated.•Provide a new mechanism explanation of the bias field by using dipole–dipole interaction.•The bias field could be adjusted by changing the thickness of the Fe50Pd50 coating layer.•The prepared FINEMET/Fe50Pd50 composite ribbons exhibit an enhanced linearity of GMI curves. 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.