Magnetic properties of the nonstoichiometric Sr-doped manganites

The chemical phase content, crystal structure, and magnetization for the doped anion-deficient La1-xSrxMnO3-x/2 (x = 0, 0.05, 0.10, 0.20, 0.30) manganites have been studied. The samples undergo the structural phase transition from the O '-orthorhombic to the rhombohedric unit cell at x > 0.10. As doping level and oxygen deficiency increase the samples show a number of magnetic transitions. In the region of 0.05 :5 x: 0.20 the samples are inhomogeneous ferromagnets while at x = 0.30 they are cluster spin glasses. The temperature of the magnetic moment freezing is similar to 45 K. The concentration dependences of the spontaneous magnetization and coercivity as well as magnetic phase diagram have been constructed. The magnetic properties of the anion-deficient Sr-doped samples may be interpreted on the basis of competition of the positive Mn3+(6)-O-Mn3+(6) and negative Mn3+(5)-O-Mn3+(6) isotropic superexchange interactions and impurity phase separation models. (c) 2005 WILEY-VCH Verlag GmbH & Co.