Effect of the Ni81Fe19 thickness on the magnetic properties of Ni81Fe19/Fe50Co50 bilayers

The effect of the Ni81Fe19 layer thickness on the magnetic and microstructural properties of Ni81Fe19/Fe50Co50 bilayers has been studied. The thickness of the Fe50Co50 layer was held constant at 15 nm, while the Ni81Fe19 layer thickness increased from 15 nm to 90 nm. This meant that the Fe50Co50 layer plus the top of the Ni81Fe19 layer were measured using a magneto-optic Kerr effect magnetometer as the laser skin depth is of the order of 20 nm. It was found that as the Ni81Fe19 layer increased in thickness the coercive and saturation fields of the bilayer structure decreased, while the effective saturation magnetostriction constant increased, towards the Fe50Co50 bulk effective saturation magnetostriction value. -- Highlights: ► Magnetostriction of 15 nm FeCo on Si is dominated by a strong interface effect ► Using a NiFe underlayer, the interface effect between the FeCo and Si is removed. ► FeCo magnetostriction constant tends towards the bulk value as the NiFe thickness increases