Effects of laser-heating on the micro-raman spectra of YBa2Cu3O7

Electrical and superconducting properties of YBa2Cu3O7 depend on the oxygen content sensitively, and the oxygen content, in turn, depends on the heating-history of the measured samples. The author reports the effects of laser heating to the micro-Raman spectra of single crystals embeded in polycrystalline YBa2Cu3O7 pellets. Form the measurements in z(xx)z-bar polarization, we found that the relative intensity of the B1g mode of the plane oxygens to that of the A1g mode of apical oxygens decreases rapidly as the laser power increases. The cause for this phenomenon is conjectured to be misalignment of micro-crystals due to thermal motion elevated by laser heating. The measurements in mixed polarization support this conjecture. (Author)