Tuning Easy Magnetization Direction and Magnetostatic Interactions in High Aspect Ratio Nanowires

Cobalt nanowires have been synthesized by electrochemical deposition using track-etched anodized aluminum oxide (AAO) templates. Nanowires with varying spacing-to-diameter ratios were prepared, and their magnetic properties were investigated. It is found that the nanowires’ easy magnetization direction switches from parallel to perpendicular to the nanowire growth direction when the nanowire’s spacing-to-diameter ratio is reduced below 0.7, or when the nanowires’ packing density is increased above 5%. Upon further reduction in the spacing-to-diameter ratio, nanowires’ magnetic properties exhibit an isotropic behavior. Apart from shape anisotropy, strong dipolar interactions among nanowires facilitate additional uniaxial anisotropy, favoring an easy magnetization direction perpendicular to their growth direction. The magnetic interactions among the nanowires were studied using the standard method of remanence curves. The demagnetization curves and Delta m (Δm) plots showed that the nanowires interact via dipolar interactions that act as an additional uniaxial anisotropy favoring an easy magnetization direction perpendicular to the nanowire growth direction. The broadening of the dipolar component of Δm plots indicate an increase in the switching field distribution with the increase in the nanowires’ diameter. Our findings provide an important insight into the magnetic behavior of cobalt nanowires, meaning that it is crucial to design them according to the specific requirements for the application purposes.

Effect of Current Density and Temperature on Template Assisted Cobalt Nanowire

Metal 1-D nanostructures are of special interest in industry applications because of their unique properties. Various synthesizing techniques have been employed to grow free standing and well dispersed nanowires. Among these methods, template assisted electrodeposition (TAE) is the most popular one because of its simplicity, cost effectiveness, high yield, ease of control over growth parameters, less contamination, and scalability to mass production. Processing conditions during the deposition process can affect the nanowire properties by a great deal. So far, these effects are not well established, and are in the early stages. In this work, we study the effect of current density and temperature on electrodeposited cobalt (Co) nanowire synthesized via template-assisted approach. Commercially available anodic alumina oxide templates were used for galvanostatic two electrode electrodeposition. Scanning electron microscopy was used to study the morphology of formed cobalt nanowires with EDS analysis confirming Co as main building element. Detailed XRD analysis was performed to find crystal orientation as well as crystal size.