Cation ordering and electrical properties of the ruddlesden-popper Gd2-2xSr1+2xCo2O7 compounds (x=0 and 0.10)

摘要

We report the structure and microstructure of the Ruddlesden-Popper (RP) series n=2 Gd2-2xSr1+2Co2O7 (x = 0 and 0.10). X-ray powder diffraction, electron diffraction and HRTEM indicate that these compounds have a tetragonal structure (space group: P4(2)/mnm) with cell parameters a approximate to 5.3749 angstrom approximate to 19.3591 angstrom, in which the [CoO6] octahedra are distorted and tilted. Also, very interestingly, according to the obtained results these compounds presents A-site cation ordering where the divalent and bigger Sr2+ cation selectively prefers the 12-coordinated P site while the smaller and trivalent Gd3+ cation prefers the 9-coordinated R site. From the electrical point of view these materials are semiconducting and their resistivitiy decreases upon doping. In addition, the highest doped sample presents a small magneto resistive effect MRmax = -3.2 % under H-max = 50 kOe at T = 5 5 K.