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

Abstract

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.

From multi-segmented to core/shell nanorods: morphology evolution in Fe–Au nanorods by tuning fabrication conditions

“…The shape anisotropy favors easy magnetization direction along the nanorods' length whereas dipolar interactions favor it perpendicular to nanorods' length. Our previous work on Co nanowires [42] indicated that center to center spacing in nanowires arrays plays decisive role to align easy magnetization direction along or perpendicular to their growth direction. The center to center spacing directly impacts packing density (magnetic content) of the nanorods arrays, that is fixed with the AAO template pore density [42].…”

“…Our previous work on Co nanowires [42] indicated that center to center spacing in nanowires arrays plays decisive role to align easy magnetization direction along or perpendicular to their growth direction. The center to center spacing directly impacts packing density (magnetic content) of the nanorods arrays, that is fixed with the AAO template pore density [42]. The estimated packing density of our templates is 12% that is much higher than the required density for the shape anisotropy to overcome dipolar interactions and hence easy magnetization direction favors perpendicular to nanorods' length [1].…”

Engineering of nickel, cobalt oxides and nickel/cobalt binary oxides by electrodeposition and application as binder free electrodes in supercapacitors

“…To obtain nanostructure coated carbon cloths, the metal nanostructures were deposited within the channels of the carbon cloth following the optimized fabrication conditions and protocols 22 , 23 which involved electrochemical deposition in the two-electrode cell with a bath volume of 20 ml. All depositions were performed at room temperature.…”

Synthesis, Development and Characterization of Magnetic Nanomaterials

“…In this Special Issue, there are research articles that focus on the thin film growth of ferromagnetic/semiconducting heterostructures and their relation to structural, magnetic, and transport properties [ 1 , 2 , 3 , 4 ], as well as Heusler alloys with ferromagnetic and Weyl semimetals behavior [ 1 , 5 ].…”