Static and dynamic spin correlations in the spin-glass phase of slightly doped La2-xSrxCuO4

Neutron-scattering experiments reveal that a diagonal spin modulation, which is a one-dimensional modulation rotated away by 45 degrees from that in the superconducting phase, occurs universally across the insulating spin-glass phase in La2-xSrxCuO4 (0.02 less than or equal to x less than or equal to 0.055). This establishes an intimate relation between the magnetism and the transport properties in the high-temperature copper oxide superconductors. Furthermore, it is found that the charge density per unit length estimated using a charge stripe model is almost constant throughout the phase diagram, even when the modulation rotates away by 45 degrees at the superconducting boundary. However. at the lowest values for I the density changes approaching 1 hole/Cu as in La2-xSrxNiO4. Magnetic excitation spectra suggest that magnetic correlations change from incommensurate to commensurate at omega similar to 7 meV and T similar to 70 K, indicating a characteristic energy for the incommensurate structure of 6-7 meV.