FIELD DISTRIBUTION IN GRANULAR, DIAMAGNETIC MATERIALS

Field distributions in samples composed of spherical, perfectly diamag netic grains, randomly dispersed in a nonmagnetic matrix, are discusse d on the basis of numerical calculations. Results of a spherical sampl e of 580 identical grains, which occupy 58% of the volume, show that ( a) the dipole moment of the sample is in good agreement with effective -medium theory predictions, (b) the superconducting volume fraction ca n be infered from its measured dipole moment, and (c) the dipole part of the actual field, to which a grain in this spherical sample is expo sed varies from 70% of the applied field (near the poles) to 130% (nea r the equator).