Structural and Magneto-Transport Properties of Copper Doped Double Layered Manganites La1.4Ca1.6Mn2O7

Samples of La1.4Ca1.6Mn2-xCuxO7 with 0 <= x <= 0.075 were prepared by a solid state reaction and characterized. The cell parameters and volume increase with increasing doped content in all the samples. The metal-insulator (MI) transition was observed in all the samples except for x = 0.075. The doping increases the MI transition temperature and resistivity. The application of a magnetic field increases the transition temperature. It can be referred to the suppression of the ferromagnetic-insulator state around it. The magnetoresistance (MR) of the undoped and 0.025 Cu-doped samples is observed on a wide range of temperatures (3.5-283 K). The undoped one exhibits a maximum value of 39.7 % at 5.07 K under 5 T. The 0.025 Cu-doped one exhibits a maximum value of 40.65 % at 44 K in the same magnetic field. No MR effect is shown for the 0.05 doped sample. The 0.075 doped sample exhibits a small negative MR behavior and a second peak of resistivity at a very low temperature.