  The two tone intermodulation distortion arising in MgB2 thin films
synthesized by hybrid physical-chemical vapour deposition is studied in order
to probe the influence of the two bands on the nonlinear response of this
superconductor. The measurements are carried out by using a dielectrically
loaded copper cavity operating at 7 GHz. Microwave data on samples having
critical temperatures above 41 K, very low resistivity values, and residual
resistivity ratio larger than 10, are shown. The dependence of the nonlinear
surface losses and of the third order intermodulation products on the power
feeding the cavity and on the temperature is analyzed. At low power, the signal
arising from distortion versus temperature shows the intrinsic s-wave behavior
expected for this compound. Data are compared with measurements performed on Nb
and YBCO thin films using the same technique.
