Morphology and magnetic properties of Co-rich Co-Pt thin films electrodeposited on Cr seed layers

Co-Pt (Pt similar to 20 atom %) alloy films were electrochemically grown at constant current density on Cr seed layers in order to study the influence of the Cr surface on their morphology and magnetic properties. The Cr seed layer favors the growth of a hexagonal close-packed phase, as revealed by X-ray diffraction. Morphological investigation using a scanning electron microscope revealed the electrocrystallization of Co-Pt on Cr to be proceeding through the nucleation and growth of three-dimensional (3D) clusters with columns growing outward in all directions from isolated nucleation centers. The 3D growth is likely due to the presence of a thin oxide layer on the Cr seed. At lower current density, individual micrometer-sized clusters were formed with distinct hexagonally shaped faces. Increasing current density results in a finer grain microstructure. At early stages of growth and low current density, the clusters exhibit a faceted morphology similar to that of the substrate. Samples prepared at higher current density or with larger thickness show larger coercivities, reaching values as high as 3490 Oe (278 kA/m) and 2275 Oe (181 kA/m) in the perpendicular and parallel directions, respectively, for a 500-nm-thick film deposited at 50 mA/cm(2). (c) 2005 The Electrochemical Society.