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Experimental and calculated dependences of granular superconductor magnetic susceptibility on the superconducting volume fraction in regimes of shielding (ZFC), Meissner effect (FC) and remanence (REM) were determined. Fractional dependences were calculated with Braggeman's asymmetric theory and allowing for the shape of superconducting grains and the sample and the influence of grain sizes upon their polarizability under different magnetization conditions. A granular superconductor with intergranular links is calculated as a three-component system, where closed clusters are regarded as superconducting particles and the function of distribution of these particles, depending on the superconducting volume fraction, is introduced. The results of calculation agree well with the experimental data in t h e ZFC regime for all fractions f = &I, but in t h e a and REM regimes for f < 0.6. The calculation for the links region gives a qualitative description of singuiarities in the experimental dependences at f > 0.6.Nomograms for determining the superconducting volume fraction in high-T, superconductors were constructed.

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The effect of magnetic flux creep on the lift force in a magnet/superconductor system was studied. It was shown experimentally that in the case of real levitation (when a levitating object bears only on a magnetic field) the suspension height and consequently the lift force did not change over a long period of time. When the levitating object is fixed for some time (i.e. a rigid constraint is imposed on it), the levitation height decreases after removal of the external constraint. It is assumed that free oscillations of the levitating object slow down the flux creep process, which is activated when these oscillations are suppressed.