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 ) 0.3 CoO 3 with x = 0.0-0.5 were studied. All samples crystallize in a rhombohedral R3̄C 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 ) 0.3 CoO 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. © 2002 Elsevier Science B.V. All rights reserved.