Giant magnetoimpedance effect of ac-dc Joule annealed electroplated NiFe/Cu composite wires

In this article, we investigate the influence of ac-dc Joule annealing of NiFe microtubes on their giant magnetoimpedance effect. NiFe magnetic layers were electroplated onto 100-mu m-diameter copper wires and then submitted to dc or ac-dc current annealing for 8 minutes. Both annealing and cooling down processes were performed in argon atmosphere. Results show that the presence of ac part of Joule treatment leads to higher induced anisotropy and increases the MI ratio. It is conjectured that the ac component through wall movement and moment fluctuation increases the tendency of the magnetic domains to lie circumferentially. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim