Magneto-transport study of intra- and intergrain transitions in the magnetic superconductors RuSr2GdCu2O8 and RuSr2(Gd1.5Ce0.5)Cu2O10

Abstract

A characterization of the magnetic superconductors RuSr2GdCu2O8 [Ru-(1212)] and RuSr2(Gd1.5Ce0.5)Cu2O10 [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 2D 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.

Submitted for Physical Review B

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Cited by in corpus (7)

• The Ruthenocuprates - Natural Superconductor-Ferromagnet Multilayers
• Critical fields and spontaneous vortex state in the weak-ferromagnetic superconductor RuSr2GdCu2O8
• I-V curves and intergranular flux creep activation energy in the magnetic superconductor RuSr2GdCu2O8
• Lower critical field and intragrain critical current density in the ruthenate-cuprate RuSr${}_2$Gd${}_{1.5}$Ce${}_{0.5}$Cu${}_2$O${}_{10}$
• Two dimensional frustrated magnetic state in superconducting RuSr2Eu1.5Ce0.5Cu2O10 (Ru-1222)
• Intergranular pinning potential and critical current in the magnetic superconductor RuSr2Gd1.5Ce0.5Cu2O10
• The upper critical field in superconducting MgB_2