High-T_{\text{c}} Superconductivity with T_{\text{c}} = 52 K under Antiferromagnetic Order in Five-Layered Cuprate Ba2Ca4Cu5O10(F,O)2 with T_{\text{N}} = 175 K: 19F- and Cu-NMR Studies

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We report on the observation of high-T_{\text{c}} superconductivity (SC) emerging with the background of an antiferro magnetic (AFM) order in the five-layered cuprate Ba2Ca4Cu5O10(F,O)2 through 19F-NMR and zero-field Cu-NMR studies. The measurements of spectrum and nuclear spin--lattice relaxation rates 19 of 19F-NMR give convincing evidence for the AFM order taking place below T_{\text{N}} = 175 K and for the onset of SC below T_{\text{c}} = 52 K, hence both coexisting. The zero-field Cu-NMR study has revealed that AFM moments at Cu sites are 0.14 \mu_{\text{B}} at outer CuO2 layers and 0.20 \mu_{\text{B}} at inner ones. We remark that an intimate coupling exists between the AFM state and the SC order parameter below T_{\text{c}} = 52 K; the spin alignment in the AFM state is presumably changed in the SC-AFM mixed state.
2011-04-15