La139 and Cu63 NMR investigation of charge order in La2CuO4+y (Tc=42 K)

We report La139 and Cu63 NMR investigation of the successive charge order, spin order, and superconducting transitions in superoxygenated La2CuO4+y single crystal with stage-4 excess oxygen order at Tstage≃290 K. We show that the stage-4 order induces tilting of CuO6 octahedra below Tstage, which in turn causes La139 NMR line broadening. The structural distortion continues to develop far below Tstage, and completes at Tcharge≃60 K, where charge …