MUON SPIN ROTATION IN <font>SR</font>₂<font>YRU</font>_1-U<font>CU</font>_U<font>O</font>₆

Abstract

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 T N ~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 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 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 ≈T N ~30 K.