PARAMAGNETIC MEISSNER EFFECT IN HIGH T-C SUPERCONDUCTORS (I) - FLUX TRAPPING IN SMALL PARTICLES AND TYPICAL BEHAVIOR OF PARAMAGNETIC MOMENTS

Theoretical and experimental results show that the state of minimum Gi nsburg-Landau free energy of small superconducting particles contains no flux line if the applied field is smaller than irs critical field. For such micron-sized particles, after being cooled in a small magneti c field (e. g. less than 100 mu T), the moment remaining during subseq uent zero field warming contains almost no contribution from trapped f lux and is dominated entirely by the paramagnetic Meissner effect (PME ) of the particles. A systematic study of such a moment has been carri ed out to reveal its characteristic behavior of temperature, magnetic field and cooling or warming rate dependence. Methods for removing and recovering the PME of small superconducting particles are also report ed.