Magnetic properties affected by structural properties of sputtered Ni/Cu multilayer films with different thicknesses of Ni layers

Abstract

Nickel-containing magnetic films have become the focus of attention due to their outstanding properties. These films are produced by many methods, including the sputtering technique. In this study, structural and magnetic properties of Ni/Cu multilayer films with different (from 92.5 nm to 17.5 nm) thicknesses of the Ni layers were investigated. The magnetron sputtering process was used to produce the Ni/Cu multilayer films. X-ray diffraction analysis showed that the films have a face-centered cubic structure with (111) plane. According to the scanning electron microscope images, while the films with the Ni layers thicknesses of 92.5 nm and 42.5 nm have some cracks and row structures on their surfaces, the films with lower thicknesses of the Ni layers have relatively more regular surfaces. As the Ni layers thickness decreased, the saturation magnetization (M-s) decreased from 617 emu/cm(3) to 387 emu/cm(3). Although the Ni/Cu multilayer with the Ni layer thickness of 92.5 nm had the highest atomic Ni content (76%); its coercivity (H-c) value was also the highest with 144 Oe. There was a decrease in the H-c value and grain size with decreasing the Ni layer thickness and the change in the H-c value can be related to the film content and surface morphology. The remanent magnetization (M-r) value changed between 492 emu/cm(3) and 105 emu/cm(3) with the reducing the Ni layers thickness. The highest M-r value and the highest M-r/M-s ratio were obtained for the Ni/Cu film with the Ni layers thickness of 42.5 nm. This Ni/Cu film has also the highest magnetization energy. The detected magnetic properties make this film desirable for permanent magnet and magnetic recording applications among the investigated Ni/Cu multilayers.