Micromagnetic simulations of magnetization reversal of iron nanowire

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Spontaneous magnetization and magnetization reversal of individual Fe nanowire with different diameter (d) and length (l) were simulated using a micromagnetic method. Results indicate that the coercivity of a Fe nanowire thinner than 20 nm approximately increases linearly with the increase of l/d ratio in the range of l/d ≤ 3, instead of 1/d2 ratio as reported in a reference, and reaches a maximum at l/d ≥ 10. At d = 6 nm and l = 200 nm, the coercivity can be as large as 1294 mT. At l = 200 nm, the reversal mechanism significantly depends on the diameter of nanowire, in the subsequence of nucleation, vortex-like nucleation and vortex with the increase of d from 6 nm to 30 nm. At l/d ≥ 10, the rectangle degree of magnetization curve exceeds 0.95, fitting the prediction for the model of infinite cylinder. The rectangle degree decreases gradually with the decrease of l/d, consistent with the reported experimental behaviors of Fe nanowires deposited on AAO templates.