Effect of the pH on the microstructure and magnetic properties of electrodeposited cobalt nanowires

The effect of the electrolyte acidity, or pH, on the structural and magnetic properties of electrodeposited cobalt nanowires has been studied. The main result is that as the pH is lowered from 3.8 down to 2.0, a microstructural change is induced. Ferromagnetic resonance measurements show that at high pH, Co presents an hcp phase with the c-axis aligned perpendicular to the wires, whereas at low pH, a more disordered hcp structure is observed. From the resonance line shape analysis, it is shown that for low-pH Co, no grains oriented with the c-axis perpendicular to the wire are present. The resulting magnetic properties show that for high-pH samples, the effective anisotropy field is weaker than that of the low-pH samples due to the competition between shape anisotropy and the cobalt c-axis magnetocrystalline anisotropy.