FAR-INFRARED MAGNETOCONDUCTIVITY OF A HIGH-T-C SUPERCONDUCTING FILM

Measurements of the far-infrared reflectivity R of a superconducting Y Ba2Cu3O7 thin film exhibit a strong dependence on magnetic field B. Th e ratios of R (B)/R(O) were used, in conjunction with a separate measu rement of R (O), to obtain the absolute values of R (B). A Kramers-Kro nig analysis then gave the field-dependent conductivity which shows a broad resonance between 50 and 250 cm(-1). A theory involving vortex m otion with pinning was able to fit the shape of the field-dependent co nductivity resonance but not the magnitude.