Cation radii and oxygen deficiency effects on the structural, magnetic, and electrical properties in La1-xSrxMnO3-delta square(delta) manganites (x=0.2-0.5 and delta=0.1)

The series of non-stochiometric strontium substituted lanthanium manganites La(1-x)Sr(x)MnO(3-delta)square(delta) (delta=0.1, x=0.2-0.5) has been studied and show the effect of oxygen deficiency on the structural transition, magnetic and electrical properties of these compounds. Polycrystalline samples La(1-x)Sr(x)MnO(3-delta)square(delta) were synthesised by a new method at atmospheric pressure. In this series of manganites, the Mn4+ content is systematically decreased due to increase in the non-stoichiometry. X-ray diffraction analysis shows a phase transition from orthorhombic to rhombohedral systems for 0.2less than or equal toxless than or equal to0.5. The material is ferromagnetic for 0.3 less than or equal to x less than or equal to 0.5 and antiferromagnetic for x = 0.2. The Curie temperature T-c increases with increasing x. The resistivity as a function of temperature shows that samples with x=0.3 and ferromagnetic metal between T-CF and T-P becomes ferromagnetic insulators below T-CF where charge-ordering seems to appear.