Tuning the magnetization reversal process of FeCoCu nanowire arrays by thermal annealing

Abstract

Arrays of hexagonally ordered Fe28Co67Cu5 nanowires with tailored diameter from 18 to 27 nm were prepared by electroplating into anodic alumina templates and annealed in the temperature range of 300-600°C, preserving but refining their bcc crystal structure. Despite the partial reduction of saturation magnetization and corresponding shape anisotropy after annealing at 500°C, larger coercivity, 0.36 T, and squareness ratio, Mr/Ms = 0.98, were obtained. This unexpected behavior is interpreted through micromagnetic simulations where the magnetic hardening is associated with the transition from vortex to transverse domain-wall reversal modes connected with the reduction of saturation magnetization. Simulations also predict a significant coercivity increase with decreasing nanowires diameter which agrees with experimental data in the overlapping diameter range. © 2013 AIP Publishing LLC.