Magnetotransport study of intra- and intergrain transitions in the magnetic superconductors RuSr2GdCu2O8 and RuSr2(Gd1.5Ce0.5)Cu2O10
S. García, J. E. Musa, R. S. Freitas, L. Ghivelder
DOI 10.1103/PhysRevB.68.144512 · Physical Review B
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Abstract
A characterization of the magnetic superconductors RuSr2GdCu2O8 [Ru-(1212)] and RuSr2Gd1.5Ce0.5Cu2O10 [Ru-(1222)] through resistance measurements as a function of temperature and magnetic field is presented. Two peaks in the derivative of the resistive curves are identified as intra- and intergrain superconducting transitions. Strong intragrain granularity effects are observed, and explained by considering the antiphase boundaries between structural domains of coherently rotated RuO6 octahedra as intragrain Josephson junctions. A different field dependence of the intragrain transition temperature in these compounds was found. For Ru-(1212) it remains unchanged up to 0.1 T, decreasing for higher fields. In Ru-(1222) it smoothly diminishes with the increase in field even for a value as low as 100 Oe. These results are interpreted as a consequence of a spin-flop transition of the Ru moments. The large separation between the RuO2 layers in Ru-(1222) promotes a weak interlayer coupling, leading the magnetic transition to occur at lower fields. The suppression rate of the intragrain transition temperature is about five times higher for Ru-(1222), a result we relate to an enhancement of the two-dimensional character of the vortex structure. A distinctive difference with conventional cuprates is the sharp increase in amplitude of the intergrain peak in both systems, as the field is raised, which is ascribed to percolation through a fraction of high quality intergrain junctions.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| RuSr2GdCu2O8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 45 | Pressure not reported | onset |
| RuSr2Gd1.5Ce0.5Cu2O10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 32.5 | Pressure not reported | onset |
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 91 | Pressure not reported | midpoint |
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