Magnetic properties of the nonstoichiometric Sr‐doped manganites

Abstract

Abstract The chemical phase content, crystal structure, and magnetization for the doped anion‐deficient La 1– x Sr x MnO 3– 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 ≤ 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 ∼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 Mn 3+ (6)–O–Mn 3+ (6) and negative Mn 3+ (5)–O–Mn 3+ (6) isotropic superexchange interactions and impurity phase separation models. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)