# Unexpected Ferromagnetism--A Review
## 2 Examples of \(d^{0}\) Ferromagnetism
### Carbon Nanostructures
#### 2.3.4 Carbon Nanotubes
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**System** & **Ref** & **Saturation Magnetization (M\({}_{\rm S}\))** & **Observations** & **Species Responsible for Ferromagnetic Behavior** \\ \hline ZnO thin film & [91] & \multicolumn{3}{c}{150 \({}^{\circ}\)C annealed:} \\  & & 0.08 emu/g & - induced defects by thermal & - singly occupied oxygen vacancy \\ ZnO thin film & [91] & 600 \({}^{\circ}\)C annealed: & annealing in argon flow & - singly occupied oxygen vacancy \\  & & 0.42 emu/g & & \\  & & at T = 300 K & & \\ \hline \multirow{6}{*}{ZnO NPs} & \multicolumn{3}{c}{Raw NPs:} \\  & & diamagnetic & - induced defects by mechanical & \\  & & after 50 h milling: & milling in diamagnetic ZnO & \\  & & 0.031 emu/g & powders & - oxygen and zinc vacancies associated \\  & & after 100 h milling & - increased density of defects leads & - intrinsic defects \\  & & 0.047 emu/g & \multicolumn{3}{c}{to increased FM order} \\  & & & 0.086 emu/g & - H\({}_{\rm c}\) = 20-90 Oe & \\  & & at T = 300 K & & \\ \hline \multirow{6}{*}{ZnO high pune (99.999%) sinithered bulk ceramics} & \multicolumn{3}{c}{50 \({}^{\circ}\)C sintered:} \\  & & 0.0183 emu/g & \multicolumn{3}{c}{H\({}_{\rm c}\) = 1300 Oe} \\  & & 850 \({}^{\circ}\)C sintered: & H\({}_{\rm c}\) = 12 Oe & - cation/anion (Zn/O) defects, as well as \\  & & 1300 \({}^{\circ}\)C sintered: & H\({}_{\rm c}\) = 34.4 Oe & - intersitials generated by sample processing \\  & & 0.00188 emu/g & & \\  & & at T = 300 K & & \\ \hline \multirow{6}{*}{ZnO Cd Gr Cd + Mn-doped NPs} & \multicolumn{3}{c}{Undoped NPs:} \\  & & D diamagnetic & The magnetization for Cd-doped & - room temperature FM (Gd-doped ZnO NP) \\ ZnO Cd Gr Cd + Mn-doped NPs & [94] & Gd-doped NPs: & NPs did not saturate at high & - possibly due to oxygen vacancy \\  & & 0.15 emu/g & magnetic fields. & - s-f coupling between ZnO and Gd ions \\  & & Gd + Mn-doped Nb: & Mn ions suppressed FM behavior. & - \\  & & 0.11 emu/g & & \\ \hline \multirow{6}{*}{ZnO Cu-doped short faceted microords or microtubules} & \multicolumn{3}{c}{Pure ZnO:} \\  & & ZnO Cu:} & \multicolumn{3}{c}{Improved M\({}_{\rm S}\) by applying a pulsed -} \\  & & 0.008 emu/g & \multicolumn{3}{c}{Imperfect field at the time} & - magnetic polarons generated by the oxygen vacancies and Cu\({}^{2+}\) ions \\  & & 2 ZnO Cu:} & \multicolumn{3}{c}{Imperfect field at the time} & - vacancies and Cu\({}^{2+}\) ions \\  & & 0.012 emu/g & \multicolumn{3}{c}{of synthesis.} \\  & & at T = 298 K & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c} \hline
**System** & **Ref** & **Saturation Magnetization (M\({}_{\rm S}\))** & **Observations** & **Species Responsible for Ferromagnetic Behavior** \\ \hline \multirow{8}{*}{TiO\({}_{2}\) films on Si substrates} & \multicolumn{3}{c}{P\({}_{\rm G2}\) = 50 m mcr.} \\  & & diamagnetic & & \\  & & \(\Gamma_{\rm O2}\) = 0.2 mcr & & \\  & & Very weakromagnetic+ & & \\  & & Dampedagnetic & & \\  & & -0.02 em/mm\({}^{\rm C2}\) & magnetic moment and the & \\  & & (-0.005 em/s) & concentration of oxygen vacancy & - & oxygen vacancies \\  & & \(\Gamma_{\rm O2}\) = 0.02 mcr & & -0.50 em/s & \\  & & (-0.075 em/s) & & \\  & & At T = 298 K & & \\ \hline \multirow{8}{*}{TiO\({}_{2}\) films} & \multirow{8}{*}{[97]} & \multicolumn{3}{c}{Anatase film:} \\  & & 2 em/cm/s & & \\  & & (-0.52 em/s) & & \\  & & Rule film & & \\  & & 6 em/cm\({}^{\rm S}\) & & \\  & & (-1.42 em/s) & & \\ \hline \multirow{8}{*}{TiO\({}_{2}\) anatase H\({}_{2}\) annealed 12 h at 600 \({}^{\circ}\)C} & \multicolumn{3}{c}{Pristine TO2} \\  & & very weak paramagnetism & & \\ \cline{1-1} \cline{3-4} \cline{6-6} \cline{6