Spin-glass behavior, spin fluctuations, and superconductivity in Sr2Y(Ru1−uCuu)O6

Abstract

Muon spin rotation measurements of Sr2Y(Ru1−uCuu)O6 (for u=0.1) reveal two distinct muon sites: one located in a SrO layer (which is superconducting at low temperatures) and the other in a Y(Ru1−uCuu)O4 layer (which is magnetically ordered at low temperatures). A precursor spin-glass state due to the Ru moments is detected in high fields (≈3.3 kOe) in Y(Ru1−uCuu)O4 layers, with a spin-glass temperature of TG=29.25K. The Y(Ru1−uCuu)O4 layers order ferromagnetically in the a-b planes at the Néel temperature, TN≈23K. This in-plane ferromagnetism alternates direction between adjacent Y(Ru1−uCuu)O4 planes, resulting in a net antiferromagnetic structure. Although the onset of superconductivity is observed both by electron spin resonance and by dc susceptibility to occur for temperatures up to about Tc,onset≈49K, this superconductivity is adversely affected by the Ru moments that fluctuate for T>TN producing magnetic fields that break pairs in the SrO layers. The muons, as well as other probes, sense the more-robust static superconductivity for T<TG. In fact, resistance measurements only show zero resistance below TN, at which temperatures the Ru moments that fluctuated for T>TN are frozen in-plane. Hence strictly speaking, the superconducting transition temperature is the same as TN, which is far below Tc,onset. Below TN there are no pair breaking fluctuating magnetic fields in the SrO layers where the hole condensate resides.

Source-reported materials — not catalogue approval

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