Influence of Cu Insertion Layer on Magnetic Properties of Co-Tb/Cu/Co-Tb Thin Films

This work focuses on the study of the influence of the insertion layer (IL) on the magnetic properties of thin films of Co-Tb. Thin films of Ta (5 nm)/Co1−xTbx (20 nm)/Cu (3 nm)/Co1−xTbx (20 nm)/Ta (5 nm) as well as Ta (5 nm)/Co1−xTbx (40 nm)/Ta (5 nm) with x = 0.10 and 0.15 were grown on a silicon substrate using DC magnetron sputtering. The X-ray diffraction patterns indicate the amorphous nature of all prepared films. The measurement of surface roughness of Ta (5 nm)/Co1−xTbx (20 nm) and Co0.85Tb0.15 (20 nm)/Cu (3 nm)/Co0.85Tb0.15 (20 nm) films using 3D optical profilometer indicates a high surface roughness. The measured out-plane and in-plane magnetic hysteresis (M-H) curves indicate that Ta/Co1−xTbx (40 nm)/Ta films (i.e., without any IL) exhibit nearly magnetic isotropic behavior. However, Ta/Co1−xTbx (20 nm)/Cu (3 nm)/Co1−xTbx (20 nm)/Ta films exhibit in-plane magnetic anisotropy. The in-plane anisotropy was found to be significant for the case of x = 0.10 film with larger effective anisotropy constant (Keff). The values of saturation magnetization and squareness (Sq) of films are found to decrease with Cu insertion layer and it is likely due to the worsening of the Co-Tb/Cu interface. The post-annealing of the Co-Tb films with Cu IL helps to improve the value of MS and Keff but it reduces the HC and the squareness of the hysteresis curve.