American Institute of Physics, Applied Physics Letters, 13(80), p. 2347
DOI: 10.1063/1.1465129
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The microwave power and frequency dependence of the surface resistance of MgB 2 films and powder samples were studied. Sample quality is relatively easy to identify by the breakdown in the ω2 law for poor-quality samples at all temperatures. The performance of MgB 2 at 10 GHz and 21 K was compared directly with that of high-quality YBCO films. The surface resistance of MgB 2 was found to be approximately three times higher at low microwave power and showed an onset of nonlinearity at microwave surface fields ten times lower than the YBCO film. It is clear that MgB 2 films are not yet optimized for microwave applications. © 2002 American Institute of Physics.