The superstructure and superconductivity of Ru1222 based RuSr2Gd2 - x - yYyCexCu2O10 - δ compounds
Abstract
For the first time, the local structure and physical properties of Ru1222 based compounds (RuSr2Gd1.4Ce0.6Cu2O10 - δ and RuSr2Gd1.8 - xY0.2CexCu2O10 (x = 0.90-0.55)) have been investigated and analyzed together on the very same compounds. The Ru1222 superstructure was confirmed by TEM at a local scale and was suggested to have an orthorhombic symmetry with space group Aba 2 and lattice parameters a_{\mathrm {s}}\simeq \sqrt {2}a , b_{\mathrm {s}}\simeq \sqrt {2}a and cs = c. This new Ru1222 superstructure distortion from tetragonal symmetry is proposed to have a positive correlation with the superconductivity variation of these compounds. The more the distortion towards orthorhombic symmetry, the higher the critical superconducting temperature these compounds can achieve. The Tc(0) of RuSr2Gd1.8 - xY0.2CexCu2O10 - δ (x = 0.85-0.55) increases monotonically from 4 to 16 K when x decreases from 0.85 to 0.70, then RuSr2Gd2Cu2O8 defects emerge and the Tc decreases with decreasing x. Ru1212 defects are observed to intergrow epitaxially with the Ru1222 structure as lamellas along the c-axis in RuSr2Gd1.4Ce0.6Cu2O10 - δ. Although Ru1212 is a superconductor, the intergrowth severely restrains its superconductivity.
- Publication:
-
Superconductor Science Technology
- Pub Date:
- November 2010
- DOI:
- 10.1088/0953-2048/23/11/115013
- Bibcode:
- 2010SuScT..23k5013T