Magnetization reversal switching in nanocylinders using dynamic techniques

Abstract

The high aspect ratio Ni nanocylinders (nanowires and nanotubes) were fabricated by means of potentiostatic electrochemical deposition in porous anodic alumina templates with pore diameter of 200 nm and a thickness of 60 µm. The growth of nanocylinders was found to depend upon deposition parameters. The structural, morphological and magnetic analysis revealed the face-centred cubic texture, uniformity and magnetic properties of nanowires and nanotubes respectively. The dynamic properties of one-dimensional uniform arrays of Ni nanowires (NWs) and nanotubes (NTs) were studied by ferromagnetic resonance technique at various frequencies ranging from 6 to 25 GHz. In particular, we identify the onset of magnetization reversal from the angular variation studies of resonance fields [Hr(θH)] and FMR linewidths [ΔHr(θH)]. Parameters such as gyromagnetic ratio (γ), damping constant (α) and effective field (Heff) were derived from theoretical fits to Hr and ΔHr data. We found that Hr and ΔHr both depend sensitively on the angle between the magnetization direction and wire-axis. For a NT geometry, the fitting of ΔHr(θH) data divulges that the magnetization reversal mechanism dominant by coherent rotation and thereafter beyond transition angle (∼80°) curling mode contributes. In case of nanowires, the curling reversal mode is the dominant magnetization reversal process.