Nondestructive Ferromagnetic Resonance Measurements Validate the Efficacy of a Seed Layer in Cobalt Magnetic Nanowire Fabrication

Abstract

Magnetic nanowires (MNWs) have been proposed for use in numerous applications due to their tunability and scale, but due to the same tunability that makes MNWs so versatile, tight quality control is needed to make the transition from research labs to industry. Currently, template-assisted electrodeposition is a promising fabrication method, but there is no quick, low-cost method to effectively quantify the fill factor (FF) of the templated wires. Here, we evaluate the efficacy of a copper seed layer to fabricate cobalt MNWs using quantitative ferromagnetic resonance (FMR). The deposition quality is assessed by FF and saturation magnetization (MS). First, the quality is evaluated by common, qualitative, or semiquantitative methods, which are then compared to the quantitative values measured from FMR. The copper seed layer is demonstrated to improve FF while maintaining MNW quality. For the seeded sample, FMR measured FF at 12.3% $\pm ~0.4$ %, with an MNW MS of $1.64~\pm ~0.10$ T. For the sample without a seed, FMR measured FF at 9.0% $\pm ~0.4$ % with an MNW MS of $1.62~\pm ~0.13$ T. These quantitative measurements were corroborated by all the qualitative and semiquantitative results, indicating that nondestructive FMR is a viable method to quantify FF and quickly evaluate the quality of templated MNWs.