Effect of Partial Substitution of Magnetic Rare Earths for La on the Structure, Electric Transport And Magnetic Properties of Oxygen Deficient Phase LaSr₂MnCrO_7-δ

摘要

Intergrowth perovskite type complex oxides La0.8Ln0.2Sr2MnCrO7-δ (Ln=La, Nd, Gd, and Dy) have been synthesized by sol-gel method. Rietveld profile analysis shows that the phases crystallize with tetragonal unit cell in the space group I4/mmm. The unit cell parameters a and c decrease with decreasing effective ionic radius of the lanthanide ion. The magnetic studies suggest that the ferromagnetic interactions are dominant due to Mn3+–O–Mn4+ and Mn3+–O–Cr3+ double exchange interactions. Both Weiss constant (θ) and Curie temperature (TC) increase with decreasing ionic radius of lanthanide ion. It was found that the transport mechanism is dominated by Mott’s variable range hopping (VRH) model with an increase of Mott localization energy.