Synthesis and characterization of the electron-doped single-layer manganite La1.2Sr0.8MnO4-delta and its oxidized phase La1.2Sr0.8MnO4+delta

The electron-doped single-layer manganite, La1.2Sr0.8MnO3.94, has been synt hesized under reducing conditions. It has the K2NiF4 type structure (space group I4/mmm) with a unit cell of a = 3.82698(2) Angstrom and c = 13.06858( 7) Angstrom. Magnetic susceptibility study of the as-synthesized sample sho ws a broad maximum at 110 K, which is attributed to an antiferromagnetic tr ansition. When the sample is treated at 550 degrees C in air, interstitial oxygen is incorporated, resulting in an oxidized phase of composition La1.2 Sr0.8MnO4.27. The oxidation results in expansion in the ab plane (a = 3.934 77(5) Angstrom) and a large contraction along the c axis (c = 12.5237(2) An gstrom). Although ferromagnetic Mn-Mn interactions are indicated at high te mperatures for La1.2Sr0.8MnO4.27, they do not lead to any long-range magnet ic order at low temperature. Instead, spin glass behavior is observed with a freezing temperature of T-f = 19.5 K. (C) 2000 Academic Press.