Structure and Magnetic Properties of Quasi-One Dimensional Cobalt-Doped Scandium Cuprate Compounds

Structure and magnetic properties of the Sc2Cu2-x CoxO5 system were investigated up to the solid solution limits x=0.4 and x=0.6. Undoped Sc2Cu2O5 has, like isostructural Y2Cu2O5, a magnetic structure with weak ferromagnetic coupling along the b-axis and strongly coupled Cu2+ chains parallel to the a-axis which were antiferromagnetically coupled below the Néel temperature of 16K. Doping with Co2+ caused the paramagnetic Curie temperature (θp) to decrease from the x=0 value of 40K, making (θp) negative for x>0.2, and caused the Néel temperature to increase to about 35K for x=0.4. Thus the interchain weak ferromagnetic coupling along the b-axis was weakened and the interchain antiferromagnetic coupling was strengthened, while the intrrchain strong ferromagnetic coupling, which displays the one-dimensional spin-spin interaction, was not influenced by the Co doping. Room-temperature structure refinement for Sc2Cu1.6Co0.4O5 from neutron powder diffraction data indicated that random substitution of Co2+ for Cu2+ occurred and that the Cu-O-O-Cu interchain superexchange pathway was enhanced by geometric changes as x increased from x=0 to 0.4.