Impedance of a thin metal film in the regime of strong magnetodynamic nonlinearity

The nonlinear response of a metallic film to the self-magnetic field of an ac transport current is investigated theoretically. The nonlinearity is due to a magnetodynamic mechanism which derives from the influence of the magn etic field of the current on the dynamics of the conduction electrons and i s most typical for pure metals at low temperatures. The nonlinearity leads to a dependence of the surface impedance on the amplitude of the ac current . It is shown that the real part of the surface impedance, which is respons ible for the Joule losses, has a smooth maximum as a function of the amplit ude. The imaginary part of the surface impedance is also a nonmonotonic fun ction of the amplitude and has a minimum. (C) 2000 American Institute of Ph ysics. [S1063-777X(00)00911-7].