Demagnetising effect in HTS in GHz frequency fields

In the present paper, we investigate the demagnetising effect in granular s uperconductors by applying the method of magnetically modulated microwave a bsorption (MMMA). The quantitative description is based on microwave measur ements of demagnetising factors in cylindrical high-temperature superconduc tors (HTS). The results prove to be in good agreement with the calculations of Chen et al. [D.-X. Chen, J.A. Brug, R.B. Goldfarb, IEEE Trans. Magnetic s 27 (1991) 3601] of demagnetising factors for cylindrical samples. The shi elding effect caused by the sample as well as by individual grains, whose i nfluence is especially noticeable for highly porous materials, is also disc ussed. The final results point to the necessity of allowing for the demagne tising effect in microwave absorption studies of superconductors. (C) 1999 Published by Elsevier Science B.V. All rights reserved.