Influences of alkaline earth metal substitution on the crystal structure and physical properties of magnetic RuSr1.9A0.1GdCu 2O8 (A = Ca, Sr, and Ba) superconductors

Abstract

We have investigated the effect of alkaline earth metal substitution on the crystal structure and physical properties of magnetic superconductors RuSr 1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) in order to probe an interaction between the magnetic coupling of the RuO 2 layer and the superconductivity of the CuO2 layer. X-ray diffraction and X-ray absorption spectroscopic analyses demonstrate that the isovalent substitution of Sr ions with Ca or Ba ions makes it possible to tune the interlayer distance between the CuO2 and the RuO2 layers. From the measurements of electrical resistance and magnetic susceptibility, it was found that, in contrast to negligible change of magnetization, both of the alkaline earth metal substitutions lead to a notable depression of zero-resistance temperature Tc (ΔTc ∼ 17-19 K). On the basis of the absence of a systematic correlation between the Tc and the interlayer distance/magnetization, we have concluded that the internal magnetic field of the RuO2 layer has insignificant influence on the superconducting property of the CuO2 layer in the ruthenocuprate. © 2005 American Chemical Society.