The effects of composition and thermal treatment on the magnetic properties of Fe100-x Co x nanowire arrays based on AAO templates

A series of Fe_100-xCo_x nanowire arrays with about 6.0 μm in length and 60 nm in diameter have been fabricated successfully by AC deposition of Fe and Co atoms into anodic aluminum oxide (AAO) templates. Samples with different composition could be obtained by adjusting the concentration ratio of Fe²⁺ and Co²⁺ in the solution of the electrolyte. The composition of the samples were determined by atomic absorption spectroscopy. Structural analysis was performed using scanning electron microscopy and X-ray diffraction. The magnetic properties of the samples were examined by vibrating sample magnetometry. The effects of composition and thermal treatment on the magnetic properties of the nanowire arrays have been examined. XRD shows that the nanowires have a body-centred-cubic (bcc) structure with a preferred orientation of the <110> axis parallel to the nanowires. When x is between 80 and 90, nanowires undergo a phase transformation α → γ which is very different from Fe–Co bulk alloy. Furthermore, a localized magnetization reversal mechanism of the nanowire arrays was conformed. It is also found that the magnetic properties of the arrays are critically dependent on the compositions and thermal treatment. With suitable choices of these factors, a kind of soft ferromagnetic film can be produced while maintaining a high coercivity and squareness.