We present a neutron scattering study of stripe correlations measured on a single crystal of La1.875Ba0.125CuO4. Within the low-temperature-tetragonal (LTT) phase, superlattice peaks indicative of spin and charge stripe order are observed below 50 K. For excitation energies ℏω ≤ 12 meV, we have characterized the magnetic excitations that emerge from the incommensurate magnetic superlattice peaks. In the ordered state, these excitations are similar to spin waves. Following these excitations as a function of temperature, we find that there is relatively little change in the Q-integrated dynamical spin susceptibility for ℏω ∼ 10 meV as stripe order disappears and then as the structure transforms from LTT to the low-temperature-orthorhombic phase. The Q-integrated signal at lower energies changes more dramatically through these transitions, as it must in a transformation from an ordered to a disordered state. We argue that the continuous evolution through the transitions provides direct evidence that the incommensurate spin excitations in the disordered state are an indicator of dynamical charge stripes. An interesting feature of the thermal evolution is a variation in the incommensurability of the magnetic scattering. Similar behavior is observed in measurements on a single crystal of La1.875Ba 0.075Sr0.050CuO4; maps of the scattered intensity in a region centered on the antiferromagnetic wave vector and measured at ℏω = 4 meV are well reproduced by a model of disordered stripes with a temperature-dependent mixture of stripe spacings. We discuss the relevance of our results to understanding the magnetic excitations in cuprate superconductors.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2004 Sep|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics