EVIDENCE OF ANTIFERROMAGNETIC ORDER IN THE GREEN PHASES DYBACUO5, YBACUO5, YBBACUO5

Magnetic susceptibility measurements between 4.2 and 300 K for R2BaCuO5 compounds (R = Dy, Y and Yb), also called "green phases," reveal the existence of antiferromagnetic ordering in the copper sublattice around 30 K. At lower temperatures χ vs. T plots show in all cases the existence of a sharp maximum, which can be attributed to the onset of antiferromagnetic ordering in the rare earth sublattice, probably induced by the polarization of Cu+2 ions. Experimental magnetic moments estimated from the Curie-Weiss region generally agree with the theoretical values expected for these R+3 ions. High-resolution transmission electron microscopy and electron diffraction experiments confirm the earlier proposed structures for the R2BaCuO5, and show the existence of a well ordered material. © 1990.