Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

Abstract

Cobalt nanowires were obtained in the process of electrodeposition into pores of an alumina membrane. Structural research (XRD, TEM) of Co revealed the facecentered cubic structure. However, the existence of the hexagonal structure cannot be excluded due to strong texture. The influences of an external magnetic field and Al 2 O 3 membrane geometry on magnetic properties of obtained wires were examined. It was found that cobalt nanowires exhibit pronounced shape anisotropy in a direction parallel to the wire axis. The highest influence on the magnetic properties is ascribed to the nanowires geometry i.e., height, diameter, and distances between single wires. Application of an external magnetic field in a perpendicular direction to the sample surface during cobalt electrodeposition increases magnetic anisotropy with a privileged direction along the wire axis. Application of the magnetic field in a parallel direction to the sample surface changes the direction of magnetization.

Influence of the electrodeposition potential on the crystallographic structure and effective magnetic easy axis of cobalt nanowires

“…The XRD patterns of Co NWs as a function of applied deposition potential are shown in Figure 3. The XRD patterns reveal that at lower applied deposition potentials, the HCP phase of Co, matching the JCPDS reference number 89-4308 (a = 2.5070 Å, c = 4.0690 Å), is predominant, with a preferred orientation along the (002) H direction, similar to other works from the literature 2, [21][22][23][24] . Thus, in this case, the NWs grow with the (002) H planes oriented along their long axis.…”

Magnetic anisotropy — How much is enough for a permanent magnet?

“…Some coercivity has been developed by depositing short wires in a microporous alumina template [41,42], but the combination of shape and magnetocrystalline anisotropy is insufficient to make a hard magnet, even though the magnetization is reduced by~60% due to the inert volume of the membrane. Template-free nanorods exhibit a magnetization similar to that of bulk cobalt, and coercivity of up to 0.89 T [43].…”

Growth Orientation Control of Co Nanowires Fabricated by Electrochemical Deposition Using Porous Alumina Templates

“…Owing to these unique characteristics and potentials, metallic nanowire arrays hold the promise to offer a wide range of rare properties for innovative applications. Examples of the interests include magnetic storage media, − nanosensors, − and electrocatalysts − and as model materials for the understanding of fundamental magnetism theories at the nanoscale. − …”