Tuning Magnetic Properties of FeNi Nanowire Arrays via Diameter Control for Self-Biased Microwave Applications

Abstract The miniaturization and integration of microwave devices such as circulators are limited by the requirement for external biasing magnets. Self-biased magnetic materials present a promising alternative, however conventional hexagonal ferrites face challenges related to high loss and integration complexity. Here, we demonstrate the fabrication of highly ordered FeNi nanowire arrays with tailored diameters using anodic aluminum oxide (AAO) templates and electrochemical deposition. By systematically varying the nanowire diameter from 20 nm to 200 nm, we observe a transition from single-domain to multi-domain magnetic structures, accompanied by a significant enhancement in coercivity and remanence in smaller-diameter nanowires. Micromagnetic simulations further reveal distinct magnetization reversal mechanisms: symmetric domain propagation in 20 nm nanowires and asymmetric vortex-domain dynamics in 200 nm nanowires. These findings provide a general strategy for designing self-biased magnetic nanowires with tunable properties, paving the way for their integration into low-loss, compact microwave systems.