# 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 c} \hline
**System** & **Ref** & **Saturation Magnetization (Mg)** & **Observations** & **Specics Responsible for Ferromagnetic Behavior** \\ \hline \multirow{8}{*}{SnO2 films on LaAlO\({}_{3}\) substrates} & & 10 nm film & & & \\  & & -27 em/cm/cm\({}^{3}\) & & & \\  & & (-3.94 em/g) & & & \\  & & 220 nm raw film & & & \\  & & -12 em/cm\({}^{3}\) & & & \\ \cline{1-1}  & & (-1.75 em/g) & & to the film’s plane & - & oxygen vacancies near the surface \\ \cline{1-1}  & & 220 nm 700 \({}^{\circ}\)C\({}_{2}\)-peak-annealed film for & & & \\  & & 10 h & & & \\  & & -4-diamagnetic & & & \\  & & At + 300 K & & & \\ \hline \multirow{2}{*}{Sr\({}_{3}\)SiO film} & \multirow{2}{*}{[105]} & \multicolumn{2}{c}{-7 em/cm\({}^{3}\)} & \multirow{2}{*}{Hc \(\sim\)75 Oe} & \multirow{2}{*}{-} & intrinsic defects \\  & & (1.48 em/g) & & - & cation vacancies \\ \cline{1-1}  & & At = 300 K & & & \\ \hline \multirow{4}{*}{CoO2 films} & \multirow{4}{*}{[40]} & For x = 0.03 & & & \\  & & -1.34 em/g & & & \\ \cline{1-1}  & & For x = 0.1 & & & \\ \cline{1-1}  & & -1.02 em/g & & & \\ \cline{1-1}  & & At = 300 K & & & \\ \hline \multirow{2}{*}{HO2 films} & \multirow{2}{*}{[106]} & \multicolumn{2}{c}{128 em/cm\({}^{3}\)} & Vacuum and air annealing clearly & - & porous structure of the film \\  & & (-13.223 em/g) & affected FM & - & oxygen vacancies \\ \hline \multirow{4}{*}{MgO films} & \multirow{4}{*}{[32]} & \multicolumn{2}{c}{-2.69 em/cm\({}^{3}\)} & \multirow{2}{*}{Reduction of Ms after annealing} & \multirow{2}{*}{-} & \\  & & (-0.751 em/g) & & & \\ \cline{1-1}  & & After annealing treatment & related to a reduction of & - & Mg cation vacancies \\ \cline{1-1}  & & 1.18 em/cm\({}^{3}\) & & Mg vacancies. & \\ \cline{1-1}  & & (-0.329 em/g) & & & \\ \hline \end{tabular}
\end{table} 
Table 1: _Cott._ \begin{table}
\begin{tabular}{c c c c c} \hline
**System** & **Ref** & **Saturation Magnetization (M\({}_{\rm S}\))** & **Observations** & **Species Responsible for Ferromagnetic Behavior** \\ \hline \multicolumn{5}{c}{_Alkaline-earth hexaborides_} \\ \hline \multirow{10}{*}{CaB\({}_{6}\) films} & \multirow{4}{*}{[107]} & Thickness 0.5 mm & \multirow{4}{*}{Increasing the thickness resulted in} \\  & & 11.36 mm/cm\({}^{3}\) & & \\  & & (\(\sim\)4.63 cm/s/g) & & \\  & & Thickness 1.6 mm & Ms decrease. & - \\ \cline{1-1}  & & 11.36 mm/cm\({}^{3}\) & & \\ \cline{1-1}  & & (-0.463 cm/s/g) & & \\ \cline{1-1}  & & Thickness 2.3 mm & contamination. & \\ \cline{1-1}  & & 0.25 emu/cm\({}^{3}\) & & \\ \cline{1-1}  & & (-0.102 emu/cm\({}^{3}\)) & & \\ \hline \multicolumn{5}{c}{CaB\({}_{6}\) crystal} & [108] & (0.12 emu/cm\({}^{3}\)) & FM mostly on/near the surface of \\ \cline{1-1}  & & (-0.0489 emu/g) & the sample & - \\ \hline \multicolumn{5}{c}{BaB\({}_{6}\) thin film} & \multirow{2}{*}{[19]} & 10.7 emu/cm\({}^{3}\) & Results ruled out contamination. & \\ \cline{1-1}  & & (-2.454 cm/s/g) & No variations due to film thickness. & - \\ \cline{1-1}  & & at T = 450-550 C & & \\ \hline \multicolumn{5}{c}{_Carbon nanostructures_} \\ \hline \multirow{10}{*}{Highly-oriented graphite samples} & \multirow{4}{*}{[79]} & ACI-HOG & \multirow{4}{*}{} & \\  & & 1.39 mmu/g & & \\ \cline{1-1}  & & AC2-HOPG & & \\ \cline{1-1}  & & 0.33 \(\pm\) 0.04 mm/g & & \\ \cline{1-1}  & & UC2-HOG & & \\ \cline{1-1}  & & 0.83 \(\pm\) 0.03 mmu/g & & \\ \cline{1-1}  & & UC3-HOG & & - \\ \cline{1-1}  & & 1.1 \(\pm\) 0.2 mmu/g & Different possibilities for the & - \\ \cline{1-1}  & & & HOG2 & FM-like behavior in the samples. & - \\ \cline{1-1}  & & 0.93 \(\pm\) 0.1 mmu/g & & \\ \cline{1-1}  & & & HOG2- & \\ \cline{1-1}  & & & HOG2- & \\ \cline{1-1}  & & 2.5 emu/g & & \\ \cline{1-1}  & & & Kish graphite & \\ \cline{1-1}  & & 0.6 \(\pm\) 0.2 mmu/g & & \\ \cline{1-1}  & & & AT = 300 K & \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._