High-temperature oxidation of Permalloy in air

Hematite (α-Fe2O3) nanowires were observed through directly annealing Ni81Fe19 foils at 600 °C for 120 min in atmosphere. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used to characterise the nanowires. The results indicate that the growing mechanism includes iron segregation to the surface combined with an internal stress induced by the oxidation process.