STRUCTURE AND PROPERTIES OF (La2-xSrx)MnO4 COMPOUNDS

Abstract

Polycrystalline single phase ( La 2-x Sr x) MnO 4 (1.10≤ x ≤1.40) samples were prepared by a citrate precursor method. They have tetragonal K 2 NiF 4 structure with a space group of 14/mmm, increasing x, unit-cell a-axis increases and c-axis decreases, which is a result of decreasing of the Jahn-Teller effect due to the increase of the Mn ( IV ) ion. Spin glass state exists at low temperature and a hump observed from the susceptibility (χ) measurement is probably caused by the interactions of several magnetic phases. Among them, ( La 0.6 Sr 1.4) MnO 4 has the largest magnetoresistance ratio ([ρ(H)-ρ(0)]/ρ(0)), which reaches to 78.4% at 48 K. It is not possible to obtain single phase materials with 0.60≤ x ≤1.00 in the heat treatment temperature range of 1000-1600°C. Impurities were easily observed under SEM and X-ray diffraction patterns. Increasing the heating period and decreasing the temperature, the amount of ABO3 perovskite phase increases. In order to extend the solubility range, of the SrO in the ( La 2-x Sr x) MnO 4, it probably needs a higher temperature (>1600°C) and a shorter heat treatment period (<1 h).