Location of the superconducting hole condensate in Sr₂YRu_1-uCu_uO₆ by μ⁺SR

The magnetic and superconducting characteristics of sintered Sr₂YRu_1-uCu_uO₆ (for u = 0.05, 0.10, 0.15) were probed using transverse- and zero-field muon-spin rotation (μ⁺SR). Since positive muons are attracted to oxygen ions in the high-T_C oxides, Sr₂YRu_1-uCu_uO₆ should (and does) present two types of μ⁺ sites, one in the YRuO₄ layers and the other in the SrO layers. The transverse- and zero-field μSR spectra for all three stoichiometries exhibit magnetic ordering at and below T_N≈30 K, with a static local field of approximately 3 kG. This transition is marked by a dramatic increase in the μ⁺ spin relaxation rate as the temperature decreases below T_N, corresponding to an increased static disordering of the magnetic moments. Above T_N no static fields are observed. Instead, the data exhibit a slow dynamic depolarization, presumably due to rapid fluctuation of magnetic moments. Both transverse- and zero-field data also indicate a smaller second component (approximately 10%) that we associate with the SrO layer, exhibiting superconducting behavior in transverse field with an observed bulk T_C≈T_N to approximately 30 K.