Effects of Ca substitution on the phonon anomalies in the Raman scattering of

Abstract

We report on the temperature dependence of the frequencies and linewidths in the phonon Raman scattering for Y1-yCayBa2Cu4O8 system (y = 0 - 0.15). The phonon anomalies above Tc of the frequencies are observed for the out-of-phase O(2)-O(3) Ag\(( \sim 340c{m^{ - 1}})\) and O(4) Ag\(( \sim 500c{m^{ - 1}})\)modes, and these onset temperatures decrease with increasing Ca content. These features are consistent with the spin-gap behaviors associated with Ca doping reported previously. Furthermore, we find that the smaller gap exists near or just above the Ba phonon frequency at \(\sim 340c{m^{ - 1}}\) in the undoped samples and its energy increases with Ca doping.