Effect of cation size and size-disorder on the magnetic and electron transport properties of La0.7−xLnxSr0.3MnO3 (Ln=Gd and Dy)

Magnetic and electron transport properties of La0.7−x Ln x Sr0.3MnO3 with Ln=Gd and Dy have been investigated over a wide range of compositions to explore the effects of the radius of the A-site cation, 〈r A〉, and the size-disorder as measured by σ 2. These manganates exhibit ferromagnetism and insulator–metal transitions up to a critical value of x (x c), with the T c (T IM) values decreasing with 〈r A〉. When x⩾x c, however, the manganates cease to be ferromagnetic and instead they show an abrupt decrease in magnetization and increase in resistivity, suggesting the likely occurrence of electronic phase separation.