Cold neutron triple-axis measurements have been used to investigate the nature of the long-wavelength spin dynamics in strongly-doped La1−xSrxMnO3 single crystals with x=0.2 and 0.3. Both systems behave like isotropic ferromagnets at low T, with a gapless (E0<0.02 meV) quadratic dispersion relation E=E0+Dq2. The values of the spin-wave stiffness constant D are large (DT=0 = 166.77 meVA˚2 for x=0.2 and DT=0 = 175.87 meVA˚2 for x=0.3), which directly shows that the electron transfer energy for the d band is large. D exhibits a power law behavior as a function of temperature, and appears to collapse as T -> T_C. Nevertheless, an anomalously strong quasielastic central component develops and dominates the fluctuation spectrum as T -> T_C. Bragg scattering indicates that the magnetization near TC exhibits power law behavior, with β≃0.30 for both systems, as expected for a three-dimensional ferromagnet.
@article{arxiv.cond-mat/9712191,
title = {Spin dynamics of strongly-doped La_{1-x}Sr_xMnO_3},
author = {L. Vasiliu-Doloc and J. W. Lynn and Y. M. Mukovskii and A. A. Arsenov and D. A. Shulyatev},
journal= {arXiv preprint arXiv:cond-mat/9712191},
year = {2009}
}