We have measured the dependence of the upper critical magnetic field upon orientation for single-crystal samples of YBa2Cu3O7 and Bi2.2CaSr1.9Cu2O8+x via four-probe resistance. We find continuous behavior of Hc2 for small deviations from parallel orientation for the Y sample, as expected for an anisotropic, three-dimensional superconductor. For the Bi sample, however, our data are more consistent with a thin-film model, exhibiting a cusp at parallel orientation, suggesting that Bi2.2CaSr1.9Cu2O8+x is a quasi-two-dimensional system.
ASJC Scopus subject areas
- Condensed Matter Physics