Doping studies of the magnetic cobaltocuprate CoSr2Y2-xCexCu2O9

A structural, magnetic and electronic study of the cobaltocuprate CoSr2Y2-xCexCu2O9 +/-delta (x = 0.5-0.8) has been performed. All materials crystallise in the orthorhombic Cmem symmetry space group in which chains of corner linked CoO4 tetrahedra run parallel to the 110 direction. An antiferromagnetic transition is observed for x = 0.5-0.8; 7 T-M increases with N. A change in the dimensionality of the magnetic order occurs at x = 0.8 as the interchain distance increases to a critical Value, There is charge transfer between the cuprate planes and cobaltate layer as Co3+ doping increases. so that Co is partially oxidised to Co with a concomitant reduction in the valence of Cu. Superconductivity is not observed in any of the samples and a crossover from Mott to Efros and Shklovskii variable range hopping behaviour is evidenced as v increases from 0,5 to 0.8, (c) 2005 Elsevier Inc. All rights reserved.