Evaluation of properties of sputtered Ni/Cu films with different thicknesses of the Cu layer

Abstract

In this study, Ni/Cu thin films with Cu layer thicknesses varying from 200 nm to absence of Cu (0 nm) were produced by using a magnetron sputtering technique in order to investigate their structural and magnetic properties. The X-ray diffraction analysis showed that the films deposited had a face-centered cubic structure and their crystallization was preferably oriented at the (111) plane. In addition, as the Cu layer thickness decreased from 200 nm to 0 nm, the intensity of fundamental Cu (111) decreased while the intensities of Ni (111) and Ni (200) increased. According to surface analysis, although pure Cu film had some specific and clear structures that were nearly spherical in form and varied in size on the surface, the film with a Cu layer thickness of 90 nm had some dark spots on the surface. The saturation magnetization (Ms) values increased with the increase of the Ni content of the films as the Cu layer thicknesses gradually decreased. Conversely, while the Cu content reduced with decreasing Cu layer thicknesses, the coercivity (Hc) values also decreased, except for the film with Cu layers thickness of 90 nm. It is possible that the dark spots seen in the scanning electron microscope image may have lowered the Hc value for the film with a Cu layer thickness of 90 nm. Thus, the production parameters of the film with a Cu layer thickness of 90 nm are optimal for obtaining multilayer films with a lower Hc value. Also, the parameters of the Ni/Cu multilayers with a Cu layer thickness of 15 nm can be considered to achieve a relatively high Ms value. In conclusion, changes in the Cu layer thickness can lead to significant alterations in the microstructural and therefore the magnetic properties.