Static and dynamic spin correlations in the spin-glass phase of slightly-doped La_{2-x}Sr_xCuO_4

Abstract

Neutron scattering experiments reveal that a diagonal spin modulation, which is a one-dimensional modulation rotated away by 45${}^{\circ }$ from that in the superconducting phase, occurs universally across the insulating spin-glass phase in La${}_{2-x}$Sr${}_x$CuO${}_4$ (0.02$\le x\le$0.055). This establishes an intimate relation between the magnetism and the transport properties in the high-temperature copper oxide superconductors. Furthermore, it is found that the charge density per unit length estimated using a charge stripe model is almost constant throughout the phase diagram, even when the modulation rotates away by 45${}^{\circ }$ at the superconducting boundary. However, at the lowest values for $x$ the density changes approaching 1 hole/Cu as in La${}_{2-x}$Sr${}_x$NiO${}_4$. Magnetic excitation spectra suggest that magnetic correlations change from incommensurate to commensurate at $\ddot{I}‰\sim$7 meV and $T\sim$70 K, indicating a characteristic energy for the incommensurate structure of 6-7 meV.

7 pages, submitted to Phys. Rev. B