Crystal structures and scaling behaviors of (La 1− xPb x)MnO 3 and La 0.7(Ba 1− xPb x) 0.3CoO 3 systems with x=0–0.5

Abstract

The magnetic properties and scaling behaviors in both series La 1− x Pb x MnO 3 and La 0.7(Ba 1− x Pb x ) 0.3CoO 3 with x=0.0–0.5 were studied. All samples crystallize in a rhombohedral R 3 ̄ C space group with a∼0.54 nm and c∼1.33 nm. The Pb 2+ substitution for La 3+ in the (La 1− x Pb x )MnO 3 system induces a mixed-valence state of Mn ions. The ferromagnetic transition temperature T C increases with increasing Pb content from 225 K for x=0 to 355 K for x=0.5 in the (La 1− x Pb x )MnO 3 series. For La 0.7(Ba 1− x Pb x ) 0.3CoO 3 samples the magnetic transition temperature is not significantly affected by the replacement of Pb ions for Ba 2+ ion and keep at about 200 K due to the constant ratio of Co 4+/Co 3+. All the samples exhibit the canonical spin-glass behaviors as well as the scaling behaviors.