EFFECT OF CD IONS ON TRANSPORT-PROPERTIES OF ORTHOMANGANITES

Magnetic and magnetotransport measurements have been used to study the compositional dependence of the electronic properties of the solid so lutions La-0.7(Pb0.3-xCdx)MnO3 and Nd-0.7(Pb0.3-xCdx)MnO3. It was foun d that these compounds are ferromagnets and have the rhombohedrally or orthorhombically distorted perovskite structure. The substitution of Pb ions by Cd leads to the transition from the metallic to the insulat ing state. The intermediate compositions exhibit two peaks of the resi stivity and magnetoresistance. The high-temperature peak is associated with the Curie temperature whereas there is no magnetic anomaly in th e temperature interval of the second peak. We suppose that Cd ions par ticipate in the formation of the narrow impurity band limiting the mob ility of charge carriers.