Shape Anisotropy and Magnetization Modulation in Hexagonal Cobalt Nanowires

Abstract

Ferromagnetic cobalt nanowires with high‐crystalline quality are synthesized using a low‐voltage electrodeposition method. High‐resolution transmission electron microscopy (HRTEM) and X‐ray diffraction (XRD) results show that the nanowires are uniform in size, and consist of predominantly hexagonal close‐packed (hcp) structure with the magnetocrystalline easy axis (c‐axis) perpendicular to the wire axis. Superconducting quantum interference device (SQUID) measurements illustrate the dominance of shape anisotropy, manifested by the weak temperature dependence of the enhanced coercive field along the wire axis. Furthermore, the magnetic structures of individual, segmented, or intersected nanowires are studied using magnetic force microscopy. This reveals a strong dipole at the two ends of the wire, together with a spatial magnetization modulation along the wire. Based on theoretical modeling, such intrinsic modulation is attributed to magnetization frustration due to the competition between the magnetocrystalline polarization along the easy axis and the shape anisotropy along the wire axis.

Magnetoresistance and exchange bias effect of the periodically nanostructured cobalt filament arrays

“…They find that the competition between the transverse crystal anisotropy and the longitudinal demagnetization energy results in spatial magnetization modulation. Moreover, this spatial magnetization modulation has a considerable influence on the MR, which has been demonstrated in cobalt nanowire by several groups [2][3][4][17][18][19]. Similarly, we suggest that the MR behaviour in the nanostructured cobalt filament arrays is controlled by the local transverse shape anisotropy created by the periodic nanostructures and the strong dipolar interaction between neighbouring elements.…”

A Universal Wet-Chemistry Route to Metal Filling of Boron Nitride Nanotubes

“…The measured regular spacing of the observed planes of the lattice is 0.210 nm, which is consistent with the interplanar spacings of (100) HCP Co. These metal@BNNT systems are potential objects for study of nanoscaled plasmonic (Ag), sensor (Pd), thermometer (In), and magnetism (Co) …”

Theory of the undulating magnetic ground state of cylindrical cobalt nanowires

“…It is the case that the period we calculate, normalized to the radius of the wire, is considerably smaller than found in the experiments reported in Ref. 12. That this is so is the case if the system parameters are close to those realized in bulk Co metals.…”

“…Earlier experimental studies reported complex domain structures in these wires but not the periodic structure displayed in Ref. 12. Possibly the domains are easily pinned by defects of various sorts.…”