# Magnetic Properties of NiZn Ferrite Nanofibers Prepared by Electrospinning
## 3 Results
In general, specific surface area is considered the main factor of the magnetization of nanoparticles due to the non-alignment of thermally fluctuating spin. Since one-dimensional nanofibers are a continuum of the smaller crystals, the influence of crystallite size and diameter must be considered. It is known that the saturation magnetization (M\({}_{\text{s}}\)) increases with the crystallite size of a crystal [44]. The crystallite sizes of our samples were estimated by the Scherrer equation. The crystallite sizes of samples A, B, and C were 20 nm, 16 nm, and 13 nm, respectively. According to this, the M\({}_{\text{s}}\) of sample A is the largest and should be gradually decreased in the order of samples B and C, but samples B and C were almost at the same levels. The saturation magnetization can be affected by several parameters, such as calcination temperature, crystal size, and crystal structure. [PERSON] et al. [45] reported that Co-doped LaSrTi oxide films obtained at low oxygen pressures had a higher M\({}_{\text{s}}\) value than those obtained at high oxygen pressure. Sample C, which had the highest PVP content, must burn more PVP during the calcination process. PVP combustion decreases the oxygen pressure, which causes more oxygen vacancies in the crystalized structure in the formation process. In sample C, the decrease in M\({}_{\text{s}}\) resulting from the small crystallite size can be compensated by the oxygen vacancies effect. The concentration of the oxygen vacancy in the samples will be measured and discussed in a future study. To verify the values of the magnetic property of samples A, B, and C, the saturation magnetization, coercivity, and remnant magnetization of each sample were summarized and compared with previous reports on NiZn ferrite nanofibers and nanoparticles. The results are shown in Table 5[8; 46; 47; 48]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{3}{c}{**Ni\({}_{0.5}\)Zn\({}_{0.5}\)Fe\({}_{2}\)O\({}_{4}\) Nanofibers**} \\ \hline \multirow{2}{*}{**Samples**} & **Maximum** & **Minimum** & **Average** & **Standard** \\  & **Diameter (nm)** & **Diameter (nm)** & **Diameter (nm)** & **Deviation (nm)** \\ \hline Sample A & 355.02 & 112.9 & 224.26 & 45.42 \\ Sample B & 391.68 & 139.66 & 245.48 & 55.78 \\ Sample C & 402.52 & 157.54 & 266.42 & 39.87 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Maximum, minimum, and average diameters, and standard deviations of Ni\({}_{0.5}\)Zn\({}_{0.5}\)Fe\({}_{2}\)O\({}_{4}\) nanofibers measured from samples A, B, and C.  
Figure 6: Magnetization versus magnetic field curves (M-H hysteresis loops) of Ni\({}_{0.5}\)Zn\({}_{0.5}\)Fe\({}_{2}\)O\({}_{4}\) nanofibers. Although the range of saturation magnetization and coercivity change varies depending on the chemical composition, such as the content of Ni and Zn ions and the heat treatment temperature, the values of samples A, B, and C were in the general range, which means that samples A, B, and C were properly fabricated by electrospinningning and the values of the magnetic property could be controlled. In the previous reports [8, 46, 47, 48, 49], the saturation magnetization and coercivity of NiZn ferrite nanofibers tended to be larger than in nanoparticles, which is thought to be due to the shape magnetic anisotropy and the small influence of thermal fluctuations.