Henkel analysis of Fe/Er multilayers prepared by electron-beam evaporation

Fe/Er multilayers were prepared by high-vacuum electron-beam evaporation system and their microstructures have been investigated. Henkel analysis was performed via isothermal remanent magnetization curve and direct current demagnetization curve. Magnetic measurement indicates that Fe/Er multilayers have an easy axis in film plane and a small value of positive magnetoresistance. It is showed that the Er layer will change to an amorphous structure when its thickness is below 3.5 nm. Hence, $Δm$ plots were established according to Henkel analysis data. The results show that $Δm$ plot has a strong dependence on the thickness of Fe and Er layers. When the thickness of Fe layer remained unchanged, $Δm$ plot indicated that the magnetic coupling was oscillating with the layer thickness; and when the thickness of Er layer was 8.8 nm, $Δm$ plot showed a positive-negative overturn of magnetic interaction, which revealed the interplay between the demagnetization and exchange coupling effect in multilayer. The explanation of $Δm$ plot was also discussed via a simplified model, i.e., a competition between demagnetizing interaction and magnetizing interaction.