The Interplay Among Electrical, Magnetic, and Structural Properties in the Non-superconducting Ru(Sr2−x Ba x )GdCu2O8±z System

Abstract

The electrical, magnetic, and structural properties of the non-superconducting RuSr2GdCu2O8±z system were studied through Ba substitution on the Sr sites. Samples of the non-superconducting Ru(Sr2−x Ba x )GdCu2O8±z system, with x=0, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50 were synthesized through the solid-state reaction method at ambient pressure, in air, at temperatures between 980 °C and 1025 °C. X-ray diffraction data show that substitution of Sr by Ba takes place iso-structurally into a tetragonal structure (space group P4/mmm, No. 123) with a solubility up to x=0.25. Rietlveld-refinement analysis indicates that the cell volume monotonically increases with barium content, while both Cu–O(1) and [1–Ru–O(1)] bond lengths, as well as the Cu–O(2)–Cu bond angles, all increase with increasing x with a maximum peak around x=0.15, and then all decrease for larger values of the barium content x, resulting into bell-type curves. The electrical resistance for the samples with 0 ≤x≤0.25 annealed in flowing oxygen at 960 °C for 2 h shows a semiconducting behavior. DC-magnetization measurements indicate that all samples exhibit ferromagnetic ordering with a magnetic transition temperature T Curie between 131 K and 141 K. Both the normalized resistance values (at a fixed temperature) and T Curie show each a similar bell-type dependence on x, a result that seems to be similar to that found for the bond lengths and angles. These five bell-type dependences on x suggest that a strong interplay among electrical, magnetic and structural properties are taken place in the non-superconducting Ru(Sr2−x Ba x )GdCu2O8±z system.