Lattice effects on the magnetic and transport properties of La0.67−xSmxSr0.33CoO3 perovskites

Abstract

Structural, magnetic, and transport properties of La0.67−xSmxSr0.33CoO3 with x=0.0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 are studied. The system exhibits a rhombohedrally distorted perovskite structure for x⩽0.10. A rhombohedral–orthorhombic structure transition is detected in the doping range from x=0.15 to 0.25 and a pure orthorhombic structure appears in sample x=0.30. When cooled, the sample shows a metal-to-metal and a metal-to-semiconductor transition subsequently, with the upper one of magnetic nature. Both resistive transitions vary against doping level, with the first one from ∼235 to ∼200 K while the second one from ∼75 to ∼175 K corresponds to a change of x from 0.0 to 0.3. The introduction of Sm drives the system from a cluster-glass state in La0.67Sr0.33CoO3 into a spin-glass state in La0.37Sm0.30Sr0.33CoO3, accompanied by an enhancement of the semiconductive character of the compounds. The absence of strong Jahn–Teller effects and the spin-state transition may be responsible for the complex lattice effects in Co-based perovskites.