engleski

Current-induced domain wall motion in spin-valve stripes with different constriction geometries

We present experimental results on the displacement of a domain wall by injection of a dc current through the wall. The samples are from 1 micron down to 0, 3 micron wide long stripes of a CoO/Co/Cu/NiFe classical spin valve structure. The stripes have been patterned by electron beam lithography. A set of two triangular-shaped constrictions are placed at 1/3 of the total length on either side of the stripe and is a pinning center for the magnetic domain wall, as shown by the steps of the giant magnetoresistance curves at intermediate levels (1/3 or 2/3) between the resistances corresponding to the parallel and antiparallel configurations. The GMR signal is used to detect the position of the domain wall along the stripe. We show by electric transport measurements that, once a wall is trapped, it can be moved by injecting a dc current higher than a threshold current of the order of magnitude of 10^7 A/cm^2. The striking result is that the direction of the domain wall displacement does not depend on the sign of the injected current. This effect has been observed at both low (3K) and room temperature, which excludes a purely thermally activated mechanism. We discuss the different possible origins of this effect, i.e. the local magnetic field created by the current and/or spin transfer exerted by the spin-polarized conduction electrons

spintronics; spin injection; domain wall motion

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