Preparation of Co-Fe-Ni alloy micropillar by microanode-guided electroplating

Microanode-guided electroplating (MAGE) was performed to prepare cobalt-iron-nickel alloying micropillars. The electrolyte was prepared by fixing [Fe²⁺] at 0.040 M and varying [Co²⁺] in 0.040–0.100 M and [Ni²⁺] in 0.30–0.60 M. The effect of bath composition on the compositional, mechanical, and magnetic properties of the alloying micropillars was investigated. Resulting from FE-SEM and EDS, all the micropillars demonstrated a smooth morphology but in different compositions depending on the bath composition. Through XRD analysis, the micropillars were characterized in nanocrystals of Co-Ni and Co₇Fe₃. After nano-indentation testing, the reduced Young's modulus of the pillars was estimated at 103.1–185 GPa and the hardness at 5.70–6.38 GPa. Investigation of all the specimens with VSM, Co₆₁Fe₂₇Ni₁₂ and Co₆₃Fe₂₅Ni₁₂ displayed the notable saturation magnetization (M_s = 180 and 175 emu/g) and the lowest coercive magnetic field (H_c = 2.1 and 1.4 Oe) among them. The mechanism of anomalous Co-Fe-Ni electrodeposition is proposed.