Effect of Al doping on the magnetic and electrical properties of layered perovskite La1.3Sr1.7Mn2−xAlxO7

The effect of Al substitution for Mn site in layered manganese oxides La1.3Sr1.7Mn2−xAlxO7 on the magnetic and electrical properties has been investigated. It is interesting that all the samples undergo a similar and complex transition with lowing temperature; they transform from the two-dimensional short-range ferromagnetic order at T*, then enter the three-dimensional long-range ferromagnetic state at TC, at last they display the canted antiferromagnetic state below TN. T*, TC and TN are all reduced with Al content. Resistivity increases sharply with increasing Al concentration, and the metal–insulator transition disappears when x reaches 10%. Additionally, magnetoresistance (MR) effect is weakened. Al substitution dilutes the magnetic active Mn–O–Mn network and weakens the double exchange interaction, and further suppresses FM ordering and metallic conduction. Owing to the anisotropic interaction in the layered perovskite, the magnetic and electrical properties are more sensitive to Al doping level than those in ABO3-type perovskite.