Abstract
We present resistivity measurements of the complete superconducting upper critical field () phase diagram as a function of angle () and temperature () for cobalt-doped epitaxial films to 0.5 K and 50 T. Although at 10 K is indistinguishable from that derived from a single-band anisotropy model, the apparent anisotropy linearly decreases to 1 at low , with . The data are well described by a two-band model with small, opposing anisotropies for the bands. This unusual relationship is confirmed by the observation of a local maximum for at low .
- Received 14 November 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.117004
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