Abstract
The far-infrared dielectric response of superlattices (SL) composed of superconducting (YBCO) and ferromagnetic (LCMO) has been investigated by ellipsometry. A drastic decrease of the free-carrier response is observed which involves an unusually large length scale of in YBCO and in LCMO. A corresponding suppression of metallicity is not observed in SL’s where LCMO is replaced by the paramagnetic metal Our data suggest that either a long-range charge transfer from the YBCO to the LCMO layers or alternatively a strong coupling of the charge carriers to the different and competitive kind of magnetic correlations in the LCMO and YBCO layers is at the heart of the observed metal-insulator transition. The low free-carrier response observed in the far-infrared dielectric response of the magnetic superconductor is possibly related to this effect.
- Received 14 March 2003
DOI:https://doi.org/10.1103/PhysRevB.69.064505
©2004 American Physical Society