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Ordered hexagonal arrays of NiFe homogeneous nanowires and NiFe/Cu multilayer nanowires were fabricated by electrodeposition into alumina membranes with pore diameter about 70 nm and 35 nm and 105 nm interpore distance, with a NiFe nanodisc thickness of 60 and 70 nm, and a Cu thickness of 50 and 10 nm. The hysteresis loops were measured with the applied magnetic field parallel and perpendicular to the wire axis using a VSM. The homogeneous NiFe nanowire array exhibits a nearly isotropic magnetic behavior. In the multilayer nanowire arrays of 70 nm diameter, the preferential direction of magnetization is perpendicular to the wire axis and the measured coercive field decreases as the t Cu / t NiFe increases. The magnetization processes in multilayer nanowire arrays of 70 nm diameter have been investigated by means of micromagnetic simulations of isolated, 2 and up to 9, wires. The magnetization distributions for the two 21(NiFe60/Cu50) and 21(NiFe70/Cu10) multilayer nanowire arrays of 70 nm diameter, with the applied magnetic field in the wire axis direction, indicate that magnetization occurs by vortex nucleation at the ends in all the wire nanodiscs. For the samples of the same composition mentioned above, but of 35 nm diameter, the reversal magnetization starts by nucleation of a domain wall. A random orientation of the magnetization in the different nanodiscs for the sample of 21(NiFe60/Cu50) can be observed. |
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