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Cation Ordering and Electrical Properties of the Ruddlesden‐Popper Gd 2−2x Sr 1+2x Co 2 O 7 Compounds (x = 0 and 0.10)
Author(s) -
SánchezAndújar M.,
SeñarísRodríguez M. A.
Publication year - 2007
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200700260
Subject(s) - tetragonal crystal system , crystallography , octahedron , magnetoresistance , materials science , divalent , high resolution transmission electron microscopy , crystal structure , diffraction , x ray crystallography , doping , chemistry , physics , nanotechnology , transmission electron microscopy , metallurgy , quantum mechanics , magnetic field , optics , optoelectronics
We report the structure and microstructure of the Ruddlesden‐Popper (RP) series n=2 Gd 2−2x Sr 1+2x Co 2 O 7 (x = 0 and 0.10). X‐ray powder diffraction, electron diffraction and HRTEM indicate that these compounds have a tetragonal structure (space group: P 4 2 / mnm ) with cell parameters a ≈ 5.3749Å c ≈ 19.3591Å, in which the [CoO 6 ] 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 Sr 2+ cation selectively prefers the 12‐coordinated P site while the smaller and trivalent Gd 3+ 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 magnetoresistive effect MR max = −3.2 % under H max = 50 kOe at T = 55 K.