Spontaneous Dewetting Morphology and Soft Magnetic Properties of Permalloy Thin Films during Thermal Annealing

A "top-down" approach for fabricating magnetic nanoparticles is reported, based on the solid-state dewetting of permalloy (Ni₈₉Fe₁₁) thin films to produce magnetically active nanoparticles adhered to SiO₂ substrates. The results demonstrate that the initial film thickness, annealing time, and annealing temperature can be precisely tuned to control the final size and morphology of the resulting nanoparticles. Furthermore, molecular dynamics (MD) simulations were employed to elucidate the nanoscale dewetting process, particularly focusing on the influence of randomly distributed vacancy defects under realistic conditions. High-resolution scanning electron microscopy and atomic force microscopy revealed distinct dewetting mechanisms for permalloy films of varying thicknesses. The evolution of magnetic properties during the dewetting stages was studied via the measurements of room-temperature hysteresis loops. This top-down fabrication strategy offers an effective means of tailoring nanoparticle size and distribution, opening new avenues for applications in magnetic materials and nanoscale devices.