Abstract
We present the electrical properties of polycrystalline La0.7−xPrxSr0.3MnO3 in which the average ionic radius of the A site 〈rA〉 is systematically varied while keeping the carrier concentration fixed. Below the Curie temperature Tc, the spin-disorder scattering process has been regarded to play an important role in the resistivity. With decreasing 〈rA〉, the structure transition from rhombohedral to orthorhombic phase accompanied with the sharp increase in resistivity at Tc and the increase of the activation energies has been observed.