119Sn Mössbauer spectroscopy in the magnetic superconductor (Ru,Sn)Sr2GdCu2O8

Abstract

The 119Sn Mössbauer spectra for the (Ru1−xSnx)Sr2GdCu2O8 system, with nominal compositions x=0.05–0.30, were measured from room temperature down to 4.2 K in samples exhibiting magnetic order followed by a resistive superconducting transition on cooling. Two contributions to the spectra are observed in the samples at room temperature: a doublet, dominating at low x, and a singlet, probably coming from the impurity phase SrSnO3. A part of the doublet evolves into a magnetic structure at low temperatures and is identified to sense the matrix properties. The isomer shift indicates that Sn enters into the RuO2 layers as Sn4+. The appearance of a magnetic phase, in the spectra, matches with the onset of the Ru-sublattice long-range order, as detected by susceptibility measurements. The area of this component exhibits a smooth decrease with the increase in the Sn content, which is well described by a random distribution in the (Ru,Sn)O2 layers. An average in-plane transferred hyperfine field of 4.29 T was sensed at 4.2 K for the sample with x=0.05, gradually decreasing with an increase in x. This high value may be indicative of the emergence of a π-phase state for the superconducting order parameter across the magnetically ordered planes, with low pair-breaking effects.

Source-reported materials — not catalogue approval

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