Magnetic Polarons in Doped La0.7Ca0.3MnO3, La0.7Ba0.3MnO3, and La0.7Sr0.3MnO3 Manganites

摘要

The characteristics of the paramagnetic state of doped manganites containing 30% Mn4+ ions are studied. It is shown that the ferromagnetic Curie temperature for the materials with chemical composition La(0.7)A(0.3)MnO(3) (A = Ca and Ba) characterized by semiconductor conductivity at T > T (C) can be determined from the measured chi(-1)(T) dependence. In the conducting La0.7Sr0.3MnO3 compound, the nonlinear behavior of chi(-1) (T) is interpreted as a result of summation of different contributions related to individual Mn ions, as well as to the paramagnetic and ferromagnetic polarons with enhanced magnetic moments. The order (first or second) of the magnetic transition and the crystal lattice symmetry do not affect the formation of correlated polarons in the paramagnetic range.