AC losses in arrays of superconducting strips on buffered metallic substrates

Full text: The effect of subdividing superconducting YBCO films on YSZ-buffered hastelloy substrates into arrays of parallel strips on the AC loss was investigated theoretically and experimentally. The hysteretic and eddy current contributions to the AC loss of such arrays were calculated as a function of temperature and applied AC magnetic field amplitude and frequency for different width and lateral separation of the strips as well as substrate and film thickness. It is shown that subdivision of a strip into sub-strips reduces the hysteretic loss proportional to the number of sub-strips. Measurements of the loss component of the AC susceptibility, X'', confirm the theoretical predictions. When the film is subdivided into N parallel strips, the frequency-independent hysteretic contribution to X'', which is dominant at lower frequencies (f ∼ 100 Hz), decreases to 1/N of its original value. As the strips become wider or their separation becomes smaller, the hysteretic X'' increases. The eddy current contribution to X'', which originates from the metallic substrate, becomes prominent as the frequency increases, approaching a linear frequency dependence at high frequencies. Its weak temperature dependence reflects that of the hastelloy resistivity