Magnetic property and structure of electrodeposited nickel on a thin niobium film

Abstract

Cyclic voltammetry, chronopotentiometry, atomic force microscopy (AFM), the magneto-optical Kerr effect (MOKE), and X-ray diffraction were used to investigate the magnetic property and the structure of thin Ni films electrodeposited onto thin Nb films. A constant-current method was used to grow the Ni films in this study. We found that β-Ni(OH)2 coexists with the Ni deposits. The Ni grains favor growing along the polar direction the very early deposition stage; they tend to grow in the lateral direction during the steady-state deposition process. The preferred orientations of the Ni deposits are fcc (111) and fcc (200); however, the easy axis of the magnetization of the Ni deposits is in the in-plane direction. Increasing the deposition current can decrease the coercivity. We used the AFM and MOKE results to determine the mechanism of the growth of the Ni deposits. We found that the growth modes of the Ni deposits in the polar and the lateral directions largely corresponded to the direct reduction of Ni and the decomposition of β-Ni(OH)2, respectively.