A-site deficiency effects on the structural and magnetic properties of La0.7Sr0.3-x□xCoO3 cobaltites

Structural and magnetic properties of La0.7Sr0.3-x□xCoO3 (0 ≤ x ≤ 0.15) samples have been investigated. Powder samples have been synthesized using the solid state reaction method at high temperature. All our samples crystallize in the rhombohedral structure with R3-bar c space group. With increasing Sr-deficiency amount, the unit cell volume decreases from 341.4 A3 (x = 0) to 338.2 A3 (x = 0.15). Our samples exhibit thermo-magnetic irreversibility behavior in the magnetization data in a magnetic applied field of 50 mT, which indicates the absence of long range ferromagnetic order. The Curie temperature decreases from 225 K (x = 0) to 180 K (x = 0.1). Sample with high deficient amount (x = 0.15) becomes predominantly spin glass phase. The effective magnetic moments values obtained from the Curie constant are close to that of the Co3+ (intermediate spin configuration) and Co4+ (low spin configuration) for 0 ≤ x ≤ 0.125 and Co3+ (low spin configuration) and Co4+ (low spin configuration) for x = 0.15