Temperature-dependent Magnetoresistance in Pr-based Manganites

[[abstract]]Systematic studies on Pr0:7Sr0:3¡ xCaxMnO3, Pr0:6Sr0:4¡ yCayMnO3, Pr0:5Sr0:5¡ zCaz MnO3, and Cr-doped Pr0:6Sr0:4(Mn, Cr)O3 reveal distinct origins of the magnetoresistance in Pr-based manganites. For Pr0:7Sr0:3¡ xCaxMnO3 and Pr0:6Sr0:4¡ yCayMnO3, the sharp enhancement of the magnetoresistance ratio (MR) around the ferromagnetic transition temperature (Tc ) indicates a percolative field-induced transition. For Pr0:5Sr0:5¡ zCazMnO3, the MR peak appears at the charge ordering temperature instead of Tc , and the low-field MR shows a different behavior from those of Pr0:7Sr0:3¡ xCaxMnO3 and Pr0:6Sr0:4¡ yCayMnO3, suggesting that the relative population of ferromagnetic and antiferromagnetic domains governs the temperature dependent MR behavior. For Cr-doped Pr0:6Sr0:4 (Mn, Cr)O3, the metal-insulator transition is shifted to a lower temperature with an enhancement of MR. Remarkably, it retains a weakly temperature-dependent character, which may be correlated with the spin scattering mechanism due to the presence of Cr-impurities.[[fileno]]2010141010040[[department]]物理