Magnetic Properties of Nanoscale Wire and Dot Systems

Abstract

Magnetic nano-wires and nano-dots were fabricated using an electron-beam lithography and liftoff technique, and the magnetic structures were controlled by engineering the size and shape. We demonstrate here the control of magnetic domain formation and domain wall movement in magnetic nano-wires, the measurement of domain wall resistance using nano-contacts between magnetic nano-wires, and the detection of magnetization reversal of the magnetic vortex core in magnetic nano-dots.1. Introduction Nanoscale magnetic systems have been attracting much attention from the fundamental and technical points of view. It is important, for the development of spin technology, to fabricate a variety of magnetic nano-patterns with the size and shape artificially controlled in high accuracy using the latest nano-patterning techniques, and to study magnetic and transport properties from a fundamental viewpoint. In this paper, we demonstrate three examples, where the magnetic structures are controlled by nanoscale patterning. The first is the control of magnetic domain formation and domain wall movement in magnetic nano-wires. It is demonstrated, by applying the giant magnetoresistance (GMR) effect to nano-wires with magnetic/nonmagnetic/magnetic layered structures, that the magnetic switching field of nano-wires can be controlled by attaching a pad at one of the two ends. The second is the measurement of domain wall resistance using nano-contacts between magnetic nano-wires. A magnetic domain wall is confined at a nano-contact and the contribution of the domain wall to the electric resistance is studied. The third is the detection of magnetization reversal of the vortex core in ferromagnetic nano-dots. The switching field of the vortex core in magnetic dots is observed using magnetic force microscopy (MFM). These series studies would lead to a development of new spin technology.

Artifacts in ballistic magnetoresistance measurements (invited)

“…Other research along these lines has also failed to find credible evidence for a real BMR effect. [17][18][19][20][21][22][23][24][25][26] These results raise the possibility that there may be no real BMR effect of any significant magnitude in any previously published data.…”

Spin-polarised currents and magnetic domain walls

“…255 in similar Ni wires as well as unpatterned Ni films. (The use of AMR and related effects to carry out nanomagnetometry is now a rather popular technique [256,257,258,259,260,261,262].) Attempts to fit the magnetoresistance data to a weak localisation model were rather unsuccessful, and the high field magnetoresistance measured in the longitudinal geometry was tentatively assigned to a modified electron-magnon scattering mechanism.…”

Nanodot and Nanorod Formation in Electron-Beam-Induced Deposition Using Iron Carbonyl

“…It is necessary to place nanodots or nanorods at desired positions for the production of such devices. Several techniques for producing nanometer-sized materials or structures have been proposed, such as mask deposition, 1) electron-beam-induced phase transition, 2) lithography, 3,4) shadow deposition 5) and self-assembly. 6) Electron-beam-induced deposition (EBID) is a promising technique for producing position-controlled nanometer-sized structures with high flexibility in their shape.…”