Fabrication And Properties Of Single Crystal Nickel Nanowire Arrays

The magnetic ordered Ni nanowire arrays have attracted much attentionbecause of their potential applications in ultrahigh density perpendicularmagnetic recording. In the present study, the Ni single crystal nanowire arrayswere successfully prepared by constant current electrodeposition. Themicrostructure of Ni nanowires was studied by employing the XRD, TEM andSAED techniques. The magnetic properties were determined by VSM. Thethermal expansion behavior was investigated by in situ high temperature XRD.The Ni single crystal nanowire arrays can be fabricated by constant currentelectrodeposition in the 0.8 mol/L NiSO₄·6H₂O electrolyte with pH value of 4.5,at a current density of 2.0 mA/cm2. The coercivity of Ni nanowire arraysincreases with the enhancement of the concentration of electrolyte, pH value andcurrent density. The optimal properties of Hc=1036 Oe and M_r/M_s=0.94 wereobtained when the diameter of nanowire is 25 nm. These good properties areattributed to the single crystal structure, which shows a large anisotropy. Thecoercivity increases from 888 Oe to 1106 Oe as the diameter reduces from 40nm to 15 nm. The thermal expansion coefficient of Ni single crystal nanowires, α=1.84×10^-5 K^-1, was determined by in situ high-temperature XRD technique,larger than that α=1.33×10^-5 K^-1 in bulk Ni.