Effect ofA-site cation size mismatch on charge ordering and colossal magnetoresistance properties of perovskite manganites

Abstract

Resistivity and ac-susceptibility measurements demonstrate that the cation size mismatch at the A site in perovskite manganites influences greatly the electrical and magnetic properties which are associated with colossal magnetoresistance. It has been reported that the Pr 1 − x Ca x MnO 3 system does not exhibit an insulator-metal transition and remains insulating at all temperatures because of charge ordering at high temperatures. We show that the cation size mismatch at the A site, introduced by replacing the Pr 3 + ions by larger La 3 + and smaller Y 3 + ions with constant average A -site ionic radius ⟨ r A ⟩ =1.18 Å, suppresses charge ordering and the samples with x =0.25 and 0.3 undergo insulator-metal transitions at 130 and 60 K, respectively, without applying a magnetic field. For 0.30 <~ x <~ 0.5, they all show a spin-glass behavior.