The measurements of linewidth of the transitions between 4f levels of Tm split by the crystal field in Y-Ba-Cu-O compounds are analyzed using the spin-wave approximation and the phenomenological approach of Millis, Monien, and Pines. It was shown that in the insulating state the main contribution to the linewidth arises from one-magnon processes and a gap in the spectrum of magnetic excitation is rather small (Δ<100 K). In superconducting compounds the main contribution to the linewidth arises from zone-center magnetic fluctuations and the temperature dependence of the linewidth is determined by static spin susceptibility.
ASJC Scopus subject areas
- Condensed Matter Physics