Determination of critical current density and effective depth of flux-pinning wells in anisotropic platelet-shaped superconductors

The magnetic moment M and the normalized creep rate S of an anisotropic platelet-shaped superconductor in the transverse magnetic field H are analyzed theoretically. The emphasis is given to the case in which angular dependences of the critical current density j(c) and the effective depth of a flux-pinning well, U-0, have peaks at theta=0 where theta is the angle between the magnetic induction B and the normal to the plane of the platelet. The analysis shows that, strictly speaking, the width of a, magnetic hysteresis loop and (1/S) are proportional not to j(c)(H) and U-0(H), respectively, but to more complex quantities, even though H exceeds considerably the self-fields of the critical currents in the sample. The manifestation of this result is the nonmonotonic H dependences of M and S for monotonically decreasing j(c)(\B\), U-0(\B\). A method for the reconstruction of j(c) and U-0 from experimental data on M and S is proposed. The obtained results must be taken into account when determining j(c) and U-0 in high-T-c superconductors with extended defects. [S0163-1829(98)03545-0].