Magnetic properties and crystal structures of self-ordered ferromagnetic nanowires by ac electroforming

We have investigated the magnetic properties and crystal structures of α-Fe and Fe21Ni79 nanowire arrays fabricated by ac electroforming into self-ordered nanosized pores in anodic aluminum oxide (AAO). The nanopores were found to have diameters of 5–100 nm and aspect ratios of 300–1000 depending on the anodization conditions. X-ray diffraction patterns provide direct experimental evidence that the α-Fe and Fe21Ni79 nanowires have preferred crystallographic orientations, indicating that those were electroformed in the (221) and (220) orientations, respectively. For the α-Fe (Fe21Ni79) nanowires, coercivity Hc and squareness Mr/Ms were found to be ∼2.02 (∼1.20) kOe and ∼0.9 (∼0.99), respectively. It is observed that the coercivity in Fe21Ni79 nanowires increased up to 1.35 kOe with increasing annealing temperature.