Reversal processes and domain wall pinning in polycrystalline Co-nanowires

Abstract

The magnetization reversal process of single Co nanowires is investigated experimentally by magnetoresistance measurements at low temperatures. The results are compared to magnetic force micrographs of the remanent domain configuration. The theoretical expectation for the reversal process is obtained from Monte Carlo simulations. We find that both the width and the thickness of the wires as well as surface scattering play a significant role for the magnetization reversal processes. While thick ͑t Ͼ 15 nm͒ and narrow nanowires ͑w Ͻ 800 nm͒ switch by domain wall nucleation at the wire ends followed by wall motion, the magnetization reversal process in wide and/or thin nanowires is achieved by the generation of a multidomain state of the magnetization. It is shown both experimentally as well as theoretically that the wire width dependence of the coercive field can be used to pin a domain wall between two wire parts of different widths.

Domain wall resistance in epitaxial Fe wires

“…Using this wire width dependence, it is possible to create artificial pinning centers by varying the wire width of a wire [19]. Fig.…”

Magnetoresistance of atomic-size contacts realized with mechanically controllable break junctions

“…The uniaxial anisotropy constant is K=6.8 X 10 5 J/m 3 where the magnitude of the anisotropy is assumed to be constant but its direction is arbitrary in the film plane reflecting the granu lar structure of the cobalt. 27 The value of the cell size 6.=7 nm corresponds to the grai n size of our sample. Each cell contains one magnetic moment.…”

Magnetization reversal and spin accumulation in nonmagnetic metals by spin injection from lateral Co/Cu, Co/Al heterojunctions

“…6 that the resistance increases less rapidly when the wide wire switches as compared to the narrow wire. This is due to the fact that for the Co2 wire the spin configuration is more complex exhibiting transverse spin components [26,27]. By applying an external field, these components will be aligned continuously along the long wire axis leading to a continuous increase of the resistance due to AMR.…”

“…1(c)) influences the switching behavior of the Co1 wire. Therefore, Monte Carlo simulations (MC) have been carried out by means of a micromagnetic model [25,26] to study the spin structure of the Co wire in more detail. Fig.…”