The magnetic and superconducting behaviors of sintered Sr 2 YRu 1-u Cu u O 6 (for u=0.05, 0.10, 0.15) were probed using transverse- and zero-field muon spin rotation (μ+ SR). In general, positive muons are attracted to oxygen ions in the high-T c oxides, and so, Sr 2 YRu 1-u Cu u O 6 should (and does) present two types of μ+ sites, those associated with the oxygen in the YRuO 4 layers and those associated with the SrO-layer oxygen. The tranverse- and zero-field data for all three stoichiometries u exhibit a sudden onset of magnetic structure at TN~30 K, with a static local field of ~3 kG. This transition is marked by a dramatic increase in the relaxation rate as the temperature decreases below TN, corresponding to an increased static disordering of the magnetic moments. Above TN no static fields are observed. Instead the data exhibit a slow dynamic depolarization, presumably due to the rapid fluctuation of paramagnetic moments. Both transverse- and zero-field data also indicate a smaller second component (~10%) which we associate with the SrO layer, exhibiting superconducting behavior in transverse field with an observed T c ≈TN~30 K.
Examples of the Application of Muon Spin Relaxation to Studies of Magnetism in Cuprates
