## 3 Results
### Magnetic Properties  
The results of magnetization measurements clarified the modifications which occurred in the magnetic structure of lanthanum manganates driven by chemical codoping by alkali elements and cobalt ions (Figure 5). The results of magnetization measurements obtained for the undoped compound indicate the inhomogeneous magnetic state with a strong ferromagnetic component which is observed for the compounds regardless the preparation procedure. The complex magnetic structure of the initial LaMnO\({}_{3}\) compound is associated with a lack in the cation content and thus the nominal excess of oxygen content leading to the formation of competing positive (Mn\({}^{3+}\)-O-Mn\({}^{4+}\)) and negative (Mn\({}^{3+}\)-O-Mn\({}^{3+}\); Mn\({}^{4+}\)-O-Mn\({}^{4+}\)) exchange interactions associated with ferromagnetic and antiferromagnetic orders, respectively. The competing antiferromagnetic and ferromagnetic phases lead to the formation of a mixed magnetic state, which is characteristic for LnMnO\({}_{3}\)-based systems [24; 42; 43; 44; 45]. Chemical substitution with alkali elements and cobalt ions leads to an increase in the magnetization of the compounds which is caused by the higher number of manganese ions having +4 oxidation state and thus leading to the strengthening of positive exchange interactions Mn\({}^{3+}\)-Mn\({}^{4+}\). Certain deviations from the above mentioned tendency were ascribed to the modification in the oxidation during the synthesis process [24] and thus to variations in the exchange interactions formed between Co and Mn ions. The powder samples codoped with sodium and cobalt ions possess the maximal value of magnetization among the compounds of both series. The difference in the magnetization at the magnetic field of 14 T of the doped compound as compared to the initial LaMnO\({}_{3}\) is about 30% (Figure 5). The observed increase in magnetization is most probably associated with the increase in the amount of Mn\({}^{4+}\) ions and the stabilization of Co ions in +2 oxidation state. The rise in the amount of Mn\({}^{4+}\) strengthens ferromagnetism in the compounds, due to positive exchange interactions Mn\({}^{3+}\)-Mn\({}^{4+}\). Simultaneously, the presence of Co\({}^{2+}\) ions causes the formation of new positive interactions Co\({}^{2+}\)-Mn\({}^{4+}\). The stabilization of the cobalt ions in +2 oxidation state is in accordance with the notable increase in magnetic anisotropy observed for the doped compound (H\({}_{\rm C}\)\(\sim\) 0.2 T for the compound La\({}_{0.9}\)Li\({}_{0.1}\)Mn\({}_{0.9}\)Co\({}_{0.1}\)O\({}_{3}\) as compared to H\({}_{\rm C}\)\(\sim\) 0.02 T of the initial compound). It should be noted that the ionic radius of the Co\({}^{2+}\) ions (0.53A for ion in high spin state and octahedral coordination) nearly coincides with the radius of Mn\({}^{4+}\) ions with the same coordination, which facilitates the occupation of \(B\)- position of the perovskite lattice. The stabilization of +2 oxidation state of the cobalt ions is also in accordance with the structural data showing a gradual increase in the unit cell volume with chemical doping. One can conclude about the optimal concentration of the amount of Mn\({}^{3+}\) and Mn\({}^{4+}\) ions in the compounds codoped with sodium (potassium) and cobalt ions which show maximal magnetization due to the dominance of strongly positive exchange interactions Mn\({}^{3+}\)-Mn\({}^{4+}\).