Synthesis of High Coercivity Cobalt Nanotubes with Acetate Precursors and Elucidation of the Mechanism of Growth

Abstract

Cobalt nanotubes (CoNTs) with very high longitudinal coercivity were prepared by electrodeposition of cobalt acetate for the first time by using anodized alumina (AAO) template. They were then characterized with X-ray diffraction (XRD), a field emission scanning electron microscope (FESEM), and a transmission electron microscope (TEM). Formation of a highly ordered hexagonal cobalt phase is observed. Room temperature SQUID (superconducting quantum interference device) magnetometer measurements indicate that the easy axis of magnetization is parallel to the nanotube axis. These CoNTs exhibit very high longitudinal coercivity of ∼820 Oe. A very high intertubular interaction resulting from magnetostatic dipolar interaction between nanotubes is observed. Thick-walled nanotubes were also fabricated by using cobalt acetate tetrahydrate precursors. A plausible mechanism for the formation of CoNTs based on mobility assisted growth is proposed. The role of the hydration layer and the mobility of metal ions are elucidated in the case of the growth mechanism of one-dimensional geometry.

On the growth mechanism of nickel and cobalt nanowires and comparison of their magnetic properties

“…The rate of reduction of metal ions thus becomes equal in both directions, resulting in nanowires. This growth mechanism is identical to the one we observed in Co NTs where acetate precursors were used for electrodeposition [25]. The XRD pattern of Ni NWs (Fig.…”

“…An understanding of the growth mechanism will help in the design of various heterogeneous structures and hybrid multifunctional nanostructures [24], and a mechanism for the formation of Co NTs using acetate precursors was proposed based on mobility assisted growth [25]. In the case of Co NTs a 5-h electrodeposition of cobalt acetate resulted in the formation of 50 μm long nanotubes.…”

“…Figure 1(b) is a schematic of the formation mechanism of the nanowires. This is based on a model involving mobility assisted growth [25].…”

Template Synthesis and Magnetic Characterization of Feni Nanotubes

“…In general, the process of electrochemical depositing of metal into the pores of the templates consists of 4 main steps: nucleation, active 1D growth, formation of "caps" on the surface of template and forming a continuous metal thin film on the surface of the template by overlap of the "caps" [30][31][32][33][34][35]. Chronoamperogramm is shown on Figure 1(a).…”

Lead free heterogeneous multilayers with giant magneto electric coupling for microelectronics/microelectromechanical systems applications

“…Another immediate application is in switching devices which can be controlled by electric and magnetic fields. MEMS/NEMS devices can also be grown by a bottom up process over silicon chip with properly designed masks (template assisted deposition 28,29 ), or can be directly fabricated starting from a nanowire synthesised by self assembly/induced assembly (non template process) and hence the synthesis can be integrated to the silicon integrated device technology. Here, a 5 step deposition is needed (lower contact electrode, BTO, CoFe, BTO, upper contact electrode) which is to be deposited over a pre fabricated mask SCHEME 2.…”