ChemInform Abstract: Preparation of Layered Manganites: Oxygen Content as a Variable Parameter of the Bilayer Compound.

Abstract

Preparation of Layered Manganites: Oxygen Content as a VariableParameter of the Bilayer Compound.-The formation temperature of bilayer compounds of general formula La 2−2x Sr 1+2x Mn 2 O 7 is found to increase from 1350 to 1500 • C with decreasing Sr content for a substitution level in the range 0.7 ≤ x ≤ 0.25. Samples with different oxygen content of the ferromagnetically ordered parent compound La 1.2 Sr 1.8 Mn 2 O 7 are prepared at an oxygen partial pressure of 10 −10 Pa. For La 1.2 Sr 1.8 Mn 2 O 7−δ the tetragonal phase is preserved up to δ = 0.27 and changes to orthorhombic symmetry at higher δ values. The Curie temp. as well as the metal-insulator transition temp. decrease with increasing δ. -(RUCK, K.; SGRAJA, M.; KRABBES, G.; DOERR, K.; MUELLER, K.-H.; KHRISTOV, M.; J. Alloys Compd. 306 (2000) 1-2, 151-157; Inst. Festkoerper-Werkstofforsch.,