Correlation between structural, transport, and magnetic properties in Sm1-xAxMnO3 (A=Sr,Ca)

Transport, magnetic, and structural properties of Sm(1-x)A(x)MnO(3), where A is Ca and Sr, have been investigated systematically over the range of doping 0 <= x <= 0.52. For x < 0.30, both systems are ferromagnetic (FM) insulator, and the resistivity (rho) can be described well by polaron hopping model. Above x=0.30, Sr-doped compounds exhibit large negative magnetioresistance (MR) in the FM metallic state and charge/orbital ordering over a narrow doping range around x=0.50. On the other hand, Ca-doped system does not show any insulator to metal transition and MR, possibly due to the smaller average A-site cationic radius < r > than that for Sr-doped one. The magnetic ground state of Ca-doped system changes from FM to canted antiferromagnetic above x=0.30. A strong coupling between transport, magnetic, and structural properties has been established from this study. The results are summarized in (x-T) phase diagrams. (c) 2007 American Institute of Physics.