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Static and dynamic spin correlations in the spin-glass phase of slightly doped La 2 − x Sr x <mml:…

2000; American Physical Society; Volume: 62; Issue: 13 Linguagem: Inglês

10.1103/physrevb.62.9148

1095-3795

M. Matsuda, M. Fujita, Kenneth M. Yamada, R. J. Birgeneau, M. A. Kastner, Haruhiro Hiraka, Y. Endoh, Shuichi Wakimoto, G. Shirane,

Magnetic and transport properties of perovskites and related materials

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 $\omega\sim$7 meV and $T\sim$70 K, indicating a characteristic energy for the incommensurate structure of 6-7 meV.