Inelastic light scattering studies of overdoped Y_1–xCa_x Ba₂Cu₃O_7–δ thin film

Abstract

The vibrational and magnetic Raman excitation spectra were examined in overdoped Y 1-x Ca x Ba 2 Cu 3 O 7-δ thin films. Below T c , certain phonons in undoped YBa 2 Cu 3 O 7-δ (YBCO) show strong self-energy effects, which gradually vanish with increasing Ca concentration into the overdoped regime. The observed B 1g symmetry two-magnon excitation peak near 2900 cm -1 in YBCO is significantly broadened, weakened, and shifts to the lower frequency with increasing Ca content, indicating the effective value of magnetic superexchange energy decreases and that the life time of the magnons becomes shorter with increasing hole concentrations.