Microwave surface resistance of nickel and zinc doped YBCO single crystals in the a-b plane

The microwave surface resistance of crystals of YBa/sub 2/(Cu/sub 1-x/M/sub x/)/sub 3/O/sub 7-/spl delta//, with M being Ni or Zn, has been systematically studied at 34.8 GHz. Both Zn (x=0.0015 and 0.0031) and Ni (x=0.0075 and 0.0140) impurities were found to be capable of lowering the surface resistance, and also substantially altering its temperature dependence. The results suggest that the microwave loss of high temperature superconducting thin films might be improved by slightly doping the material with impurities.<
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