Nonuniform paramagnetic state in nonstoichiometric lanthanum manganites La$_{1-x}$Mn$_{1-y}$O$_{3}$

The magnetic properties of nonstoichiometric lanthanum manganites La$_{1-x}$Mn$_{1-y}$O$_{3}$ have been studied in the temperature range 80 K $<T<$ 650 K. The Curie temperature $T_C$ changes nonmonotonically as the number of Mn$^{4+}$ ions increases. In the paramagnetic region, there exist isolated Mn ions and magnetic polarons which can be conserved to $T\le$ 4$T_{C}$, independent of the lattice symmetry. In the $T_{C}<T<T_{\operatorname{pol}}$ region, the temperature dependences of the magnetic susceptibility are nonlinear and can be described by the Curie law with a temperature-dependent Curie constant $C$. The sample has been prepared having a composition near the O' $\to$ O structural transition; the spontaneous magnetization of the sample at $T\le$ 1.6$T_{C}$ is associated to correlated polarons forming due to the double exchange in chains of the $E$-type antiferromagnetic phase.