Eur. Phys. J. B 20, 35-54

Magnetic anisotropy and domain patterns in electrodeposited cobalt nanowires

Y. Henry¹, K. Ounadjela¹, L. Piraux², S. Dubois³, J.-M. George⁴ and J.-L. Duvail<sup>5

1</sup>  Institut de Physique et Chimie des Matériaux de Strasbourg (CNRS UMR 7504) and Université Louis Pasteur, 23 rue du Loess, 67037 Strasbourg Cedex, France
²  Département des Sciences des Matériaux et des Procédés, Université Catholique de Louvain, Place Croix du Sud 1, Louvain la Neuve 1348, Belgium
³  Laboratoire de Métallurgie Physique (CNRS UMR 6630) and Université de Poitiers, 86960 Futuroscope Cedex, France
⁴  Laboratoire Central de Recherches Thomson (CNRS/Thomson-CSF UMR 137) , Domaine de Corbeville, 91404 Orsay, France
⁵  Institut des Matériaux de Nantes (CNRS UMR 6502) and Université de Nantes, 2 rue de la Houssinière, 44322 Nantes Cedex 03, France

yves.henry@ipcms.u-strasbg.fr

(Received 14 September 2000)

Abstract
The magnetic anisotropy and domain structure of electrodeposited cylindrical Co nanowires with length of 10 or 20 m and diameters ranging from 30 to 450 nm are studied by means of magnetization and magnetic torque measurements, as well as magnetic force microscopy. Experimental results reveal that crystal anisotropy either concurs with shape anisotropy in maintaining the Co magnetization aligned along the wire or favours an orientation of the magnetization perpendicular to the wire, hence competing with shape anisotropy, depending on whether the diameter of the wires is smaller or larger than a critical diameter of 50 nm. This change of crystal anisotropy, originating in changes in the crystallographic structure of Co, is naturally found to strongly modify the zero (or small) field magnetic domain structure in the nanowires. Except for nanowires with parallel-to-wire crystal anisotropy (very small diameters) where single-domain behaviour may occur, the formation of magnetic domains is required to explain the experimental observations. The geometrical restriction imposed on the magnetization by the small lateral size of the wires proves to play an important role in the domain structures formed.

PACS
75.50.-y - Studies of specific magnetic materials.
75.30.Gw - Magnetic anisotropy.
75.60.Ch - Domain walls and domain structure.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001

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