## 3 Results and Discussion
### Morphological Analysis  
Figure 3a-d represents the HR-FESEM images of all the samples. Figure 3a shows the wires formed in the absence of a magnetic field (Ni-Non-Magnetic sample) with relatively shorter length. A noticeable surface roughness is also observed, in these cases. The effect of an external applied magnetic field during synthesis has been observed on the length, average diameter and surface roughness of the wires. The wires suspended in solution oriented themselves along the field direction. The length of the wires increases in the samples to which a magnetic field was applied, constituted by long arrays, which can be observed in Figure 3b-d. Average length and average diameter were measured  
Figure 1: Schematic showing arrangement of magnets to create magnetic field with different shapes, with a magnetic field of 500 Gauss. Below the strength of the magnetic field exposed to the solution, due to the shape of the magnet, is shown.  
with Image J software. The average lengths of the wires were found to have increased from 28.04 \(\upmu\)m, for Ni-Non-Magnetic, to 62 \(\upmu\)m for Ni-Double wires, 58 \(\upmu\)m for Ni-Single wires and 59 \(\upmu\)m for Ni-Ring wires. However, the diameter of the wires was observed to significantly decrease, by 3.0 \(\upmu\)m for Ni-Non-Magnetic wires, by 1.36 \(\upmu\)m for Ni-Double wires, by 1.28 \(\upmu\)m for Ni-Single wires and by 1.55 \(\upmu\)m for Ni-Ring samples, as displayed in Figure 2c along with their standard deviations. As seen in Figure 2b,c, these values are in well agreements with those of FWHM calculated through XRD analysis. The lowest FWHM was found for Ni-Non-Magnetic, which led to the highest average diameter, and the highest FWHM was observed for Ni-Single wired and led to the smallest average diameter. This shows that the application of a magnetic field during synthesis helps reduce wires' diameter and enhance their length. The smallest diameter was observed for Ni-Single wires. Nevertheless, in the cases of Ni-Double and Ni-Ring wires, the diameters of the wires were less than those observed for Ni-Non-Magnetic wires. Further, the effect of the shape of the magnetic field was observed to influence the roughness of the wires. Ni-Single wires, in addition to showing the smallest diameters, also exhibited the least roughness, as compared with the other conditions, while the greatest surface roughness was found in Ni-Ring wires. Small particles can be distinctly observed on the surface of the Ni-Ring wires, accounting for their enhanced surface roughness. It appears that the particles constituting these wires were not arranged along the axis of the wire and but rather formed protrusions in several directions, due to the ring-type arrangement of the magnet generating the magnetic field, compared to the partial effect on the solution by other magnets. Moreover, the shape of the magnetic field was also found to affect the quantity of the final product. The Ni-Ring sample produced a relatively smaller amount as compared with the other samples. Thus, the lowest diameters, longest lengths and smoothest surfaces were all found in the Ni-Single wires.  
Figure 2: (**a**) XRD patterns of Ni-Non-Magnetic, Ni-Double, Ni-Single and Ni-Ring; (**b**) the values of FWHM calculated from XRD patterns; and (**c**) the average diameters of the Ni-wires. Error bar shows the standard deviation.