Power and magnetic field-induced microwave absorption in Tl-based high T c superconducting films

Abstract

The increase in the microwave surface resistance Rs of high Tc superconductors at elevated microwave power levels is reported for both oriented and unoriented Tl-based films as a function of rf magnetic field at 820 MHz and 18 GHz. The application of dc magnetic fields produces qualitatively similar increases in Rs and in the surface reactance Xs. The increase in Rs with dc field is shown to arise from simple decoupling of grains by intergranular magnetic flux. The increase in Rs with microwave power, on the other hand, is a consequence of hysteretic intergranular processes.

Superconducting stripline model of intergranular flux penetration

“…For p, << ol, [the limit opposite to equations (15)], equation (12) is z,, = z, +"m a which is the classical skin depth limit. Portis et [7] for T1-based films and Hein et a1 181 for electrophoretically deposited layers of YBa2C~307.~ have extensively studied the magnetic field dependence of the microwave surface impedance. In neither case was it possible to take Zeff to the limit of equation ( 16).…”

Origin of nonlinear surface impedance and intermodulation distortion in YBa2Cu3O7−x microstrip resonator

“…One is the input power dependence of the surface impedance Z s ϭR s ϩiX s , [1][2][3][4][5][6][7][8] in which R s is the surface resistance and X s is the surface reactance. The other is the intermodulation distortion ͑IMD͒ generation [9][10][11][12] or the harmonic generation.…”

“…13,14 The origin of nonlinear Z s has been discussed in many articles. [4][5][6][7][8] In discussing the origin of nonlinear Z s , the results of experiments cannot be simply compared because they involve differences in conditions such as film quality and resonator structure. As indicated by Golosovsky et al, 8 there is no universal mechanism of nonlinear electrodynamics of superconductors.…”

The microwave power handling of an FIB-generated weak link in a YBCO film

“…The presence of weak-links in granular material can give rise to diverse dependence of surface resistance upon microwave magnetic field. In this context, weak links are usually modeled in terms of the resistively shunted junction (RSJ) model [1,2,3,4,5,6]. Oates et al performed a control experiment using a stripline resonator geometry with an edge junction and found that the weak link followed an RSJ type behaviour [7].…”