Tunable magnetic properties in evaporated Co-Sm/Fe-Sm bilayer films by crystalline states of under-layer and high magnetic field

Bilayer is an effective structure to enhance magnetic properties of films. This study employs high magnetic field (HMF) and amorphous Fe-Sm under-layer to tune the magnetic properties of evaporated Co-Sm/Fe-Sm bilayer films. Various analysis methods are used to explore the relation of microstructure evolution under above conditions with magnetic performance. The results show that both the amorphous Fe-Sm under-layer and the HMF can decrease surface roughness. Further, the HMF exhibits other effects that reduces column size, increases interplanar spacing and affects interface at atomic scale. The structural variation has effect on magnetic properties of bilayer films. The amorphous Fe-Sm under-layer increases magnetization, coercivity and squareness through changing the amount of non-magnetic structure at atomic scale. Meanwhile, the HMF decreases coercivity by changing pinning via the interface variation. Both the HMF and amorphous under-layer have no influence on the anisotropy of bilayer films. These results present an effective method to tune the magnetic properties of films through amorphous under-layer and HMF.