Electrodeposited hard-magnetic Fe50Pd50 nanowires from an ammonium-citrate-based bath

Abstract

Fe–Pd nanowires were synthesised in anodic alumina templates by applying both potentiostatic and pulsed electrodeposition regimes. When using potentiostatic deposition, only fragmented nanowires were obtained; however, the use of pulse deposition was shown to be effective for producing solid nanowires. In order to achieve this, different on-times for the deposition and off-times between the pulses in an electrolyte with a constant concentration of Fe(III) and Pd(II) ions at pH 9 were employed. Homogeneous nanowires with the composition Fe55±5Pd45±5, lengths of 2.5μm and diameters of 200nm were synthesised under the following pulsed conditions Eon=−1.4V, ton=2s and Eoff=−0.1V, toff=10s for 5000 cycles. The as-deposited nanowires had a fcc crystal structure and were magnetically soft (HC≈5kA/m) with the easy axis of magnetization perpendicular to the long axes of the nanowires, mainly due to the dipolar coupling within the template. In order to promote the ordering into the L10 phase, annealing in the temperature range 400–700°C for 1–9h in Ar+7% H2 was performed. The highest coercivity of 122kA/m was achieved by annealing at 600°C for 5h.