Community Research and Development Information Service - CORDIS

G3 = Magnetic domain structures in single metal nanowires

Experimental investigations have revealed a drastic change in the magnetic anisotropy properties of hcp Co nanowires upon varying their diameter. As the wire diameter is reduced below 40-50nm the preferential orientation of the crystal easy axis of magnetization (c-axis) changes from perpendicular to parallel to the wire axis. This strongly affects the zero field magnetic domain structure which form in the nano-wires.

For small diameters, both shape anisotropy and crystal anisotropy favour an alignment of the magnetisation along the wire axis. As a consequence, the magnetisation is oriented longitudinally and a single domain structure can be realized after applying a saturating magnetic field along the wire. After the application of a transverse saturating field, the magnetic configuration consists of a succession of several longitudinally magnetized anti-parallel domains. Due to the severe lateral confinement of the magnetisation, these domains are forced to meet head-on, which never occurs in bulk material.

In nanowires with large diameters, a single domain state cannot be achieved in zero field, although the very elongated shape of the objects favors such a magnetic configuration. Instead, complex multidomain patterns always form in zero field, in which the domain magnetisation has a strong transverse component. This results from a competition between the shape anisotropy and the crystal anisotropy which tends to align the magnetisation normal (or almost normal) to the wire axis.

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