Correlation between structural, transport, and magnetic properties in Sm_1−xA_xMnO₃ (A=Sr,Ca)

Abstract

Transport, magnetic, and structural properties of Sm_1−xA_xMnO₃, 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 (ρ) 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.