Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic Resonance

摘要

We report detailed ~(17)O, ~(139)La, and ~(63,65)Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La_(1.875)Ba_(0.125)CuO_4 single crystal and in oriented powder samples of La_(1.875)Ba_(0.125)CuO_4. We observe a partial wipeout of the ~(17)O NMR intensity and a simultaneous drop of the ~(17)O electric field gradient (EFG) at low temperatures where the spin stripe order sets in. In contrast, the ~(63,65)Cu intensity is completely wiped out at the same temperature. The drop of the ~(17)O quadrupole frequency is compatible with a charge stripe order. The ~(17)O spin lattice relaxation rate shows a peak similar to that of the ~(139)La, which is of magnetic origin. This peak is doping dependent and is maximal at x ≈ 1/8.