Study on the Structural, Electrical and Magnetic Properties of the ${\rm Ru}({\rm Sr}_{2-{\rm x}}{\rm Ba}_{\rm x}){\rm GdCu}_{2}{\rm O}_{8\pm{\rm z}}$ System

Samples of the Ru(Sr
_2-x
Ba
_x
)GdCu
₂
O
_8±z
system, with x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50 were prepared through solid-state reaction at ambient pressure at 980-1025°C. From the X-ray diffraction (XRD) patterns, it was observed that the substitution of Sr by Ba takes place iso-structurally into a tetragonal structure (space group P4/mmm). Rietveld refinement analysis indicates that both Cu-O(1) and Ru-O(1) bond lengths strongly depend on Ba content. The temperature dependence of the electrical resistance for the samples with 0.0 ≤ × ≤ 0.25 annealed in flowing oxygen at 960°C for 2 hrs. show a semiconducting behavior, whereas samples annealed during 30 hrs. present a semiconducting-to-metal transition. Results of the DC magnetic susceptibility measurements on samples annealed for 2 hrs. indicate that all samples exhibit ferromagnetic ordering, with magnetic transition temperature T
^Currie
that depend on Ba content with a dependence that seems to be similar to one found for the bond lengths.