Quantitative study of the effect of current density on the morphological and magnetic domain structures of electrodeposited nanocrystalline cobalt films

Abstract

We have investigated quantitatively the morphological and magnetic domain structures of nanocrystalline cobalt films electrodeposited at different current densities in the range from 40 to 50mA/cm2. The films had the thickness of about 40μm and were prepared at room temperature from a cobalt sulfate solution with pH value of 4.5. The morphological structure of the films was revealed by atomic force microscopy (AFM), whereas the magnetic domains were imaged with the colloid-scanning electron microscopy (colloid-SEM) method. The morphological structure consisted of densely packed grains with irregular shapes. No geometric alignment and no preferred elongation of the grains were observed on the film surface. The magnetic domain structure was composed of maze and surface domains with magnetization perpendicular to the film surface. As the deposition current density was increased from 40 to 50mA/cm2, the average grain size decreased from 81 to 71nm and the average domain size increased from 320 to 410nm. The films crystallized mainly in the hexagonal close-packed (HCP) phase with the hexagonal axis perpendicular to the film surface. The crystallographic texture is found to decrease with decreasing grain size.