Magnetic and transport properties of some insulating manganites

The magnetic and transport properties of $A_{1-x}{\mathrm{Pb}}_x{\mathrm{MnO}}_{3-x}{\mathrm{F}}_x\hspace{0.5em}(A=\mathrm{L}\mathrm{a},\mathrm{}\mathrm{Nd}),$ ${\mathrm{La}}_{0.66}{\mathrm{Ba}}_{0.34}\left({\mathrm{Mn}}_{1-x}{\mathrm{Nb}}_x\right){\mathrm{O}}_3,$ ${\mathrm{La}}_{0.85}{\mathrm{K}}_{0.15}\left({\mathrm{Mn}}_{1-x}{\mathrm{Nb}}_{1-x}\right){\mathrm{O}}_3,$ ${\mathrm{La}}_{0.82}{\mathrm{K}}_{0.18}\left({\mathrm{Mn}}_{1-x}{\mathrm{W}}_x\right){\mathrm{O}}_3,$ and ${\mathrm{BiMnO}}_3$ insulating manganites with perovskite structure have been investigated. It was established that a number of compounds show ferromagnetic behavior and large magnetoresistance in spite of the absence of four-valent manganese ions. It is shown that magnetic and transport properties can be explained in terms of the mechanism of superexchange interactions via anions, taking into account the charge localization on magnetic and chemical disorder.