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

The electron-doped single-layer manganite, La1.2Sr0.8MnO3.94, has been synthesized 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 shows a broad maximum at 110 K, which is attributed to an antiferromagnetic transition. When the sample is treated at 550 degrees C in air, interstitial oxygen is incorporated, resulting in an oxidized phase of composition La1.2Sr0.8MnO4.27. The oxidation results in expansion in the ab plane (a = 3.93477(5) Angstrom) and a large contraction along the c axis (c = 12.5237(2) Angstrom). Although ferromagnetic Mn-Mn interactions are indicated at high temperatures for La1.2Sr0.8MnO4.27, they do not lead to any long-range magnetic order at low temperature. Instead, spin glass behavior is observed with a freezing temperature of T-f = 19.5 K. (C) 2000 Academic Press.