Origin of coercivity and high-frequency magnetic properties in patterned Co₉₀Nb₁₀ thin films

Stripe-patterned Co 90 Nb 10 thin films were prepared using electron beam evaporation with controlled stripe widths (30–80 μm) to explore the interplay between geometric patterning and magnetic behavior. Systematic analysis revealed distinct mechanisms governing coercivity: longitudinal coercivity (along the stripe length) was predominantly influenced by surface roughness-induced domain wall pinning, whereas transverse coercivity (along the width) depended on geometric modulation of demagnetizing fields. Atomic force microscopy and profilometry confirmed uniform film thickness (50 nm) and minimized surface roughness (0.278 nm) at an optimal stripe width of 60 μm. Magnetic characterization demonstrated in-plane anisotropy, with easy-axis coercivity reaching a minimum of 20.4 Oe at 60 μm, inversely correlated with surface smoothness. High-frequency measurements revealed tunable resonance frequencies (2.33–3.01 GHz) and peak initial permeability (407) at 60 μm, driven by balanced anisotropy fields and reduced pinning effects. These findings underscore the critical role of stripe geometry in tailoring magnetic performance, providing a scalable strategy for optimizing soft magnetic films in high-frequency devices such as inductors and sensors.