THE MIDINFRARED CONDUCTIVITY DETERMINED FROM THE INFRARED REFLECTANCEOF YBA2(CU1-XNIX)3O7-DELTA FILMS

We present the midinfrared conductivity of a YBa2(Cu0.94Ni0.06)3O7-del ta film determined from fitting the measured infrared reflectance with a two-component model. To a first approximation, the ''best-fit'' mid infrared band conductivity is independent of T, in agreement with the midinfrared band used previously to fit the reflectances of films with less-than-or-equal-to 4% Ni. For the best fits, the midinfrared band at 10K and 100K has a well defined maximum at 300 cm-1. This feature d isappears at 300K and its spectral weight is redistributed up to about 1000cm-1. Above about 1000cm-1, the midinfrared band is independent o f temperature.