Frequency dependent magnetization of superconductor strip

The frequency dependence of magnetic ac loss of thin superconductor strip subjected to an ac magnetic field perpendicular to the surface of the strip is investigated by incorporating a flux creep model into the critical state model of Brandt and Indenbom. It is found that the reduced ac loss exhibits a maximum value at a frequency f(m), which is a rapidly varying function of the applied ac magnetic field. At low magnetic field, f(m) becomes zero, and ac loss decreases with frequency as a power law (similar to f(-2/n)). Whereas at high magnetic field f(m) becomes infinite and ac loss increases with frequency, still following the power law (similar to f(1/n)). The analytical results are substantiated with experimental data and the results of a 2D finite element simulation.