## 3 Results
### Magnetic Properties
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & **Mn Oxidation State (\%)** & \multicolumn{2}{c}{**Co Oxidation State (\%)**} \\ \cline{2-5}  & **3+** & **4+** & **2+** & **3+** \\ \hline  & & Powders & & \\ \hline La\({}_{0.9}\)Li\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 73.2 & 26.8 & 61.1 & 38.9 \\ La\({}_{0.9}\)Na\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 75.2 & 24.8 & 42.9 & 57.1 \\ La\({}_{0.9}\)K\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 67.2 & 32.8 & 39.9 & 60.1 \\ \hline  & & Ceramics & & \\ \hline La\({}_{0.9}\)Li\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 75.8 & 24.2 & 60.2 & 39.8 \\ La\({}_{0.9}\)Na\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 65.1 & 34.9 & 41.7 & 58.3 \\ La\({}_{0.9}\)K\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) & 66.3 & 33.7 & 37.0 & 63.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Oxidation state of Mn and Co ions in synthesized powders and ceramics. It should be noted that the magnitude of magnetization observed for the compound codoped with Li and Co ions is notably lower than the magnetization observed for other doped compounds in the powder form. The coercivity of the compound codoped with Li and Co ions is about 40% larger than the values observed for other doped compounds, which indicates a larger amount of the cobalt ions in +2 oxidation state as confirmed by XPS measurements. Examining isothermal magnetization dependences, one can assume that the magnetic state of the Li- and Co- codoped compounds is determined by the coexistence of positive exchange interactions formed between Co\({}^{2+}\)-Mn\({}^{4+}\) ions and negative interactions Mn\({}^{3+}\)-Mn\({}^{3+}\) and Co\({}^{2+}\)-Mn\({}^{3+}\). The ceramic compounds are characterized by a lower value of magnetization as compared to the related powder samples, which is caused by a reduced amount of oxygen content occurring during the high pressure procedure, as indirectly confirmed by the EDS and XPS data. The smaller amount of oxygen content results in the increase in the number of structural defects, which frustrates exchange interactions thus leading to the mixed magnetic state. As in the case of the compounds in the powder form, chemical doping leads to the stabilization of +2 oxidation state of the cobalt ions, which leads to an increase in the value of coercivity. The stabilization of cobalt ions in +2 oxidation state leads to an increase in the magnetization of the compounds doped with sodium (lithium) and cobalt ions, which can be caused by the formation of positive exchange interactions Co\({}^{2+}\)-Mn\({}^{4+}\) ions. Magnetization estimated for the potassium and cobalt codoped compound is notably lower in comparison to the other codoped compounds, especially in the low field region, which can be explained by a more distinct reduction in oxygen content that occurred in these compounds during the high pressure procedure. The deficit in the oxygen content frustrates the dominant long-range ferromagnetic order, thus reducing spontaneous magnetization; moreover, an increase in the amount of oxygen vacancies provides negative Mn\({}^{3+}\)-Mn\({}^{3+}\) and Co\({}^{2+}\)-Mn\({}^{3+}\) interactions and thus fosters the stabilization of the mixed magnetic state characteristic of the initial LaMnO\({}_{3}\) compound (Figure 5). The nonsystematic evolution of magnetization observed for the ceramic compounds can be explained by the absorption of oxygen by a sample holder during high pressure treatment. The formation of nanoscale crystallites with an average size of a few tens of nanometers, due to the application of high pressure, causes  
Figure 5: Isothermal magnetization curves measured for the initial LaMnO\({}_{3}\) and codoped La\({}_{0.9}\)A\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) (A: Li, Na, K) powders (**left**) and ceramics (**right**) at T = 5 K (the graphs presented using the same scales).