Template‐based Synthesis and Characterization of High‐density Ferromagnetic Nanowire Arrays

Abstract

This chapter covers the synthesis and characterization of magnetic nanowire arrays that are grown inside nanoporous templates. Applications for such arrays include patterned recording media, magnetic and acoustic sensors, and other avant‐garde applications that will be envisioned once the fundamental properties and performances of these arrays are better known. Several nanoporous templates are introduced, but this chapter primarily focuses on results using anodic alumina templates. The templates are filled with ferromagnetic metals via electrodeposition either using DC deposition onto an electrode after the removal of a barrier oxide or using AC deposition to eliminate the need to remove the oxide. Several typical electrolyte recipes are given (Co, Fe, FeGa alloys, Ni, and NiMn), and the details of both techniques are discussed. Methods for controlling the magnetic properties of the arrays by the choice of nanowire material, diameter, and interpore spacing, in addition to external fields, are detailed. Next, numerical simulations are presented in order to investigate the switching behavior of magnetic nanowires. Perfect hexagonal arrangements of pores on a square centimeter scale are demonstrated using imprint lithography. Finally, the applications of recording and sensors are discussed in detail.

Surface Morphology and Magnetic Properties of Isolated Cylindrical Nickel Nanowires

“…This is expected since the nanowires are very small compared to the laser spot size and the scattering effect. Importantly, the shapes of the hysteresis loops are quite different from those of two dimensional arrays of nanowires reported in the literature [6,37,44,51]. There is also, a change in the shape of the loop and a reduction in the coercivity as the external magnetic field is changed from parallel to the perpendicular direction.…”

“…As a result, squared shaped hysteresis loops were obtained when the magnetic field was applied along their long axial direction. In contrary, the hysteresis loops for two dimensional arrays of Ni nanowires seen in literature showing the perpendicular direction as an easy axis of magnetisation [6,37,44,51]. This is solely due to the strong magneto-static interaction between the nearest nanowires, which makes the perpendicular direction of the templated nanowires is easy to magnetise.…”

“…These nanowires have many interesting properties that are not seen in a bulk or three dimensional structures. Therefore, fabrication and characterisation of such structures present interest from both fundamental and industrial points of view [14,16,28,29,37,44,51,58]. As an example; they may play a significant role in future applications, in particular; ultra-high density magnetic storage devices in hard disc drives and volatile magneto resistive random access memory (MRAM) [28][29].…”

Electrochemical and galvanic fabrication of a magnetoelectric composite sensor based on InP

“…This enables the use of a several hundred microns thick piezoelectric layer, resulting in a higher magnetoelectric voltage coefficient. Galvanic filling of a membrane structure is much simpler than galvanic pore filling and a well established technique [4-6]. From basic principles, it is clear that it is not possible to etch curro-pores through the complete InP wafer.…”

Magnetoelectric polymer nanocomposite for flexible electronics

“…Deposition pulses were negative with current density limit of À60 mA/cm 2 , and separated by positive polarization pulses and relatively long rest pulses to refresh the ion concentrations for homogenous deposition. 10 The ferromagnetic Fe NWs were 6 lm of length and 35 nm in diameter. Finally, Fe NWs were released from the membrane by dissolving the template membrane.…”