High magnetic field studies of YBa/sub 2/Cu/sub 3/O/sub 7/ and NdBa/sub 2/Cu/sub 3/O/sub 7/ single crystals

The authors have measured the upper critical magnetic field H/sub c2/ of single crystals of the high-T/sub c/ superconductors YBa/sub 2/Cu/sub 3/O/sub 7/ and NdBa/sub 2/Cu/sub 3/O/sub 7/ as a function of crystal orientation in DC fields up to 31.5 T. The temperature dependence and anisotropy of H/sub c2/ and inferences concerning spin-orbit scattering are discussed. The lowest value of critical field is obtained for the crystal orientation which makes the applied field perpendicular to the Cu-O planes and is not much different from the values of H/sub c2/ for some conventional superconductors.<
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