An 17O NMR study of the Cu-O planes of Bi2Sr2Ca2Cu3O10

Temperature dependent NMR shift and spin-lattice relaxation times have been measured for 17O from the two distinct Cu-O planes of the n=3 phase of Bi2Sr2Can-1CunO10. Both sites show a marked, but different, temperature dependence of NMR shift above Tc (107 K in zero field). The shift for the 17O resonance associated with the central Cu-O plane starts to decrease from ∝300 K and the spin component of the Knight shift has dropped to ∝1/2 of its room temperature value by Tc. For the outer planes the 17O shift is almost temperature independent until 120 K when it decreases sharply and the spin component of the Knight shift is ∝2/3 of its room temperature by Tc. The different temperature dependence of the 17O shift of the outer two Cu-O planes from that of the 17O of the central plane shows there is little coupling between planes. The relaxation behaviour for both sites is probably Korringa-like (Ks2T1T is constant) in the normal state with the value of Ks2T1T being close to the theoretical value for simple s-type metals with no electron-electron interaction. (orig.)