Upper critical field of the magnetic superconductor RuGd1.4Ce0.6Sr2Cu2O10−δ

Abstract

We performed measurements of magnetic susceptibility, electrical resistivity, and magnetoresistance in magnetic fields of up to 18 T in the magnetic superconductor RuGd1.4Ce0.6Sr2Cu2O10−δ synthesized in oxygen pressures up to 95 atm. The magnetic-susceptibility data show the occurrence of an antiferromagnetic state below TN∼175K, followed by the development of a weak ferromagnetic state near TM∼100K, and followed further by the onset of superconductivity (SC) at Tc∼42K. The electrical resistivity as a function of temperature shows an evolution from nonmetal-to-SC behavior in samples prepared in a flux of O2 to a well defined metal-like behavior in samples prepared under 95 atm pressure of O2. The electron-phonon coupling constant was calculated from transport data to be λtr∼0.17, a value comparable with other cuprates, indicating weak electron-phonon coupling in these ruthenates. The values of the upper critical field Hc2 for the O2 high-pressure treated samples were obtained from the magnetoresistivity data yielding Hc2ab(0)∼39T, and the out-of-plane superconducting coherence length ξc(0)∼28Å. Based on the similarities between these ruthenates and the superconductor YBa2Cu3O7−δ, we estimated Hc2c(0)∼8T and ξab(0)∼140Å. We used these parameters to discuss the coexistence of long-range magnetic order and superconductivity on a microscopic scale on these materials.

Source-reported materials — not catalogue approval

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