In our previous works, the magnetic levitation force acting on a superconducting single crystal was devided into two parts. The first part, for magnetic field less than the first critical field( Hc1) of the superconducting sample, is explained by using the Meissner effect and is reversible. The second part, for magnetic field larger than He1, is explained by using the Bean's critical state model and is irreversible. For grain size larger than the penetration depth (λ) of the superconducting material, one would expect that larger grain will give larger irreversible part in magnetic levitation force measurement. Experiments were done on epoxy-YBCO samples of ratio 1.3 in mass with four different grain sizes. Results come out as expected. We also have fitted the experimental curves for different grain size with our previous model calculations. Theoretical results agree with experimental measurements quite well.
Physica C: Superconductivity and its Applications 282-287(3), pp.1455-1456