Sol-gel synthesis and properties of tin-doped lanthanum manganites

The crystallographic, magnetic, electrical, and magnetoresistive properties of samples of La 0.775 Sr 0.225 Mn 1 − x Sn x O 3 synthesized by the sol-gel method are studied. It is shown that introducing tin atoms, with their large size, into the manganese sublattice produces significant deformations of the crystal lattice and enhances the structural and magnetic inhomogeneity of the samples. It is discovered that increasing the tin content leads to a reduction in magnetization, a lowering of the Curie temperature, and an increase in the electrical resistivity. The way the crystallographic parameters change is found to correlate with the character of the changes in the magnetic parameters. It is shown that the low-temperature magnetoresistance increases with x , while the magnetoresistance around room temperature is a nonmonotonic function of the tin concentration and has a maximum at x = 0.015 .