Differences in the Magnetic Properties of Co, Fe, and Ni 250−300 nm Wide Nanowires Electrodeposited in Amorphous Anodized Alumina Templates

Anodized alumina membranes (AAMs) were synthesized by a three-step electrochemical anodization of aluminum. The anodization results in a hexagonally pseudo-ordered 2D array of nanochannels. The AAMs were used as templates to grow Ni, Co, and Fe nanowires, with diameters in the range of 250−300 nm, by electrodeposition. The AAM appears to be amorphous, while the metal nanowires are polycrystalline. The angular dependence of the coercivity, H C, of the Ni nanowires presents a smooth variation from a μ o H C = 5.5 mT when the field is applied perpendicular to the wires to μ o H C = 53 mT when the field is applied parallel to them. However, the Co and Fe nanowires exhibit a peak in the angular dependence of H C for fields applied close to the AAM plane (i.e., perpendicular to the wires). The competition between shape anisotropy and dipolar interactions between the nanowires seems to be responsible for the difference in magnetic behavior between the different metals.