Nickel Nanowire Arrays Research Articles

Synthesis of ultrahigh-density ordered arrays of metallic nickel nanowires in mesoporous silica films.

Two-dimensional (2D) mesoporous silica films were employed as a template to fabricate ultrahigh-density ordered arrays of metallic nickel nanowires via electroless deposition.

Micropolarizer of Ordered Ni Nanowire Arrays Embedded inPorous Anodic Alumina Membrane

A micropolarizer of nickel nanowire arrays within ananodic alumina membrane (AAM) was fabricated by anodization of pure Aland electrodeposition of Ni, respectively. X-ray diffraction, scanningelectron microscopy and transmission-electron microscopy reveal thatthe nanowires are polycrystal and have an average diameter of 70 nm.Spectrophotometer measurements show that the nickel nanowire arraysembedded in the AAM can only transmit polarized light vertical to thewires. An extinction ratio of 25 to 30 dB and an average insertion lossof 1.07 dB in the wavelength range of 1-2.5 µm were obtained,respectively. Thus, Ni nanowire/AAM can be used as a wire grid typemicropolarizer.

Switching behavior of single nanowires inside dense nickel nanowire arrays

Summary form only given. The suitability of nickel nanowire arrays for perpendicular magnetic storage media with areal densities beyond the superparamagnetic limit (>70 Gbit/in/sup 2/) is analyzed in this paper. Highly ordered alumina pore channel arrays are used as templates for the fabrication of magnetic nanowire arrays with a periodicity of 65 (180 Gbit/in/sup 2/) and 100 nm (75 Gbit/in/sup 2/) and pore diameters between 30 and 55 nm. A nearly perfect hexagonal arrangement for the magnetic columns occurs only inside very narrow process windows for periodic distances of 65, 100 and 500 nm, and - in contrast to most publications in this field - a degree of pore filling of almost 100% was achieved. Here, we will focus on nickel as a filling material due to its negligible magneto-crystalline anisotropy, so that the interactions between the anisotropy resulting from the nanowire shape and the stray field inside the magnetic arrays can be studied in detail. The small magnetic moment and the large exchange lengths (/spl lambda//sub ex/= (A/2K/sub 1/)/sup 05/ /spl ap/ 20 nm) of nickel leads to low dipole interactions between nanowires and a huge anisotropy along the column axis which enables nickel as a suitable material for pattern perpendicular magnetic media.

Ferromagnetic resonance studies of nickel and permalloy nanowire arrays

Arrays of nickel and permalloy nanowires have been studied by ferromagnetic resonance for frequencies ranging from 10 MHz up to 40 GHz using a micro-strip transmission line. Measurements of the transmission coefficient show intense resonance peaks which exhibit a pronounced dependence on the frequency-field values. The interplay between the angular-field resonance frequency and the material parameters has been studied in detail. It is shown that by changing the wire packing density, the dispersion relation can change from strongly dependent to quasi-independent behavior as a function of the applied field direction. This effect is explained in terms of the dipolar coupling between wires and its competition with the wire shape anisotropy.

Spin-wave quantization in ferromagnetic nickel nanowires.

The dynamical properties of uniform two-dimensional arrays of nickel nanowires have been investigated by inelastic light scattering. Multiple spin waves are observed that are in accordance with dipole-exchange theory predictions for the quantization of bulk spin waves. This first study of the spin-wave dynamics in ferromagnetic nanowire arrays reveals strong mode quantization effects and indications of a subtle magnetic interplay between nanowires. The results show that it is important to take proper account of these effects for the fundamental physics and future technological developments of magnetic nanowires.

Magnetic anisotropy in prismatic nickel nanowires

Nickel nanowire arrays with a diamond-shaped cross section and the same orientation have been fabricated in nanoporous single mica crystal membranes by electrodeposition. All wires are 5 μm long with an effective diameter of 120 nm. The sample can be considered as a collection of laterally and vertically aligned identical micromagnetic prisms. We report on the magnetic anisotropy due to the quasi-one-dimensional wire shape and diamond cross section.

Hexagonally ordered 100 nm period nickel nanowire arrays

The magnetic behavior of 100 nm period arrays of Ni nanowires embedded in a highly ordered alumina pore matrix were characterized by magnetometry and magnetic force microscopy. Reducing the diameter of the nanowires from 55 to 30 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 to 1200 Oe and to increasing remanence from 30% to 100%. The domain structure of the arrays exhibits in the demagnetized state a labyrith-like pattern. These results show that stray field interactions of single domain nanowires are entirely dependent on the nanowire diameter.

Array of nickel nanowires enveloped in polyaniline nanotubules and its magnetic behavior

An array of nickel nanowires enveloped in polyaniline nanotubules was prepared by the “second-order-template” method. As the first step, an array of the polyaniline nanotubules was synthesized in the pores of an alumina membrane, then nickel nanowires were fabricated by electrochemical deposition of the nickel into the polyaniline nanotubules. The composite nanostructure was characterized by x-ray powder diffraction, and scanning electron micrography. Its magnetic properties were measured by a vibrating sample magnetometer. The coercivity and remanence are of high anisotropy with a maximum at θ=90° (parallel to the nanowires).

Dipolar interactions in arrays of nickel nanowires studied by ferromagnetic resonance

Using a planar microstrip transmission line, the dipolar interactions in electrodeposited Ni nanowires arrays are characterized as a function of the membrane porosity (4% to 38%) and the wire diameter (56 to 250 nm). The dipolar interactions between the wires can be modeled in a mean-field approach as an effective uniaxial anisotropy field oriented perpendicular to the wire axis and proportional to the membrane porosity. The dipolar interaction field opposes the self-demagnetization field of an isolated single wire which keeps the magnetization parallel to the wire axis. An increase in the porosity therefore induces a switching of the effective anisotropy easy axis from parallel to perpendicular to the wire axis above a critical porosity of 35-38% independent of the wire diameter.

High Density Hexagonal Nickel Nanowire Arrays with 65 and 100 nm-PERIOD

AbstractHighly ordered alumina pore channel arrays are used as templates for the fabrication of magnetic nanowire arrays. These well-defined templates are based on the approach by Masuda and Fukuda and have an interpore distance of 65 and 100 nm and a monodisperse pore diameter of ≍30 nm. The pore channels are hexagonally arranged in 2D-domains, which extend over more than ten interpore distances. Nearly 100% metal filling of the alumina pore structures is obtained by a novel pulsed electrodeposition technique. Due to the high ordering degree of the nanowires arrays, we detect a squareness of ≍100% and coercive fields of 1200 Oe in the direction of the nanowires. The MFM measurements have been carried out by applying magnetic fields on magnetized and demagnetized samples to study the switching behavior of individual nanowires inside the arrays. Magnetic wires have been locally switched by a strong MFM tip and a variable external magnetic field. The MFM results show a good agreement with the bulk magnetic hysteresis loops.

Uniform Nickel Deposition into Ordered Alumina Pores by Pulsed Electrodeposition

Ordered arrays of nickel nanowires have been prepared using pulsed electrodeposition. Two self-patterning anodization processes were used to fabricate alumina pore matrices into which nickel was deposited from a Watts bath: two short millisecond deposition pulses followed by a long delay yielded almost 100 % filled pores (see Figure). Nanowire arrays are expected to have important applications as magnetic memories.

Finite-size effects in nickel nanowire arrays

Nickel nanowire arrays with diameters in the range 30–500 nm have been fabricated by electrochemical deposition into nanoporous, single-crystal mica templates, which allow measurements of the magnetic properties of nickel nanowire arrays at high temperatures. The Curie temperature is found to be reduced by as much as 51 K for the 30 nm diameter nanowires. The Curie temperature shift with wire diameter follows the finite-size scaling relation with l50.94 and j0522 A.

Fabrication of nanoporous single crystal mica templates for electrochemical deposition of nanowire arrays

Nanopores with lateral dimensions as small as 33 nm have been fabricated by nuclear track etching in 5 μm thick, single crystal mica wafers. The nanopores have a diamond shape with their axes aligned with the crystal axes of mica as a result of anisotropic etching. Nickel nanowire arrays with a constant volume fraction have been fabricated by electrodeposition into the nanopores. The magnetic properties of the nickel nanowire arrays in the mica templates are reported.

Magnetic Properties of 100 NM-Period Nickel Nanowire Arrays Obtained from Ordered Porous-Alumina Templates

AbstractNi nanowires were grown in highly-ordered anodic alumina templates using pulsed electrodeposition. This technique yields completely metal-filled alumina membranes. The magnetic behavior of 100 nm period arrays of Ni nanowires with a length of 1 μ and different diameters has been characterized using SQUID magnetometry and magnetic force microscopy. Reducing the diameter from initially 50 to 25 nm while keeping the interwire distance constant leads to increasing coercive fields from 600 Oe to 1200 Oe and to increasing remanence from 30% to 100% of the hysteresis. The deposition of Ni65Fe35 gave a further improvement of the coercive fields up to 1350 Oe.

Electrochemical deposition of nickel nanowire arrays in single-crystal mica films

Nanopores with lateral dimensions as small as 30 nm have been fabricated by nuclear track etching in 5 μm thick, single-crystal muscovite mica wafers. The nanopores have a diamond shape with their axes aligned with the crystal axes of mica as a result of anisotropic etching. Nickel nanowire arrays have been fabricated by electrodeposition into the nanopores. The magnetic properties of the nanowire arrays are compared with those fabricated in polymer membranes.

Fabrication and Magnetic Properties of Arrays of Nickel Nanowires

Arrays of nickel nanowires are fabricated by electrochemical deposition into template-Anopor. The wires have high aspect ratio L/D=250, with diameter 200nm and length 50m. The easy axis is perpendicular to the nanowire because of the static magnetic interaction between the neighbouring nanowires.

Structural, Magnetic Properties of the Electrochemically Deposited Arrays of Nickel Nanowires

ABSTRACTThe room temperature structural, magnetization and magnetoresistive properties of Ni-nanowires of diameters 18, 30 and 78 nm and various lengths, fabricated by electrochemical deposition of Ni in the nanopores of anodic alumina, are investigated. The crystallographic orientation depends on the diameter of nanowires. Nanowires show perpendicular magnetic anisotropy and enhanced coercivity (Hc) and remanent magnetization (Mr) values of up to 500 Oe and 50% respectively. An electrodeposited Ni-layer (5 μm) on copper substrate shows in plane magnetic anisotropy and the Hc and Mr values are 97 Oe and 37%. Ni-nanowires and Ni-layer show an anisotropic magnetoresistive behaviour.

Fabrication and Magnetic Properties of Arrays of Metallic Nanowires

Arrays of ferromagnetic nickel and cobalt nanowires have been fabricated by electrochemical deposition of the metals into templates with nanometer-sized pores prepared by nuclear track etching. These systems display distinctive characteristics because of their one-dimensional microstructure. The preferred magnetization direction is perpendicular to the film plane. Enhanced coercivities as high as 680 oersteds and remnant magnetization up to 90 percent have also been observed.