Vortex-lattice characteristics measured inside a hollow YBaCuO superconducting cylinder

Hollow YBaCuO superconducting cylinder has been placed in a d.c. magnetic field H≤1200 Oe creating a mixed state in the sample and a.c. magnetic field h≤1 Oe applied to its outer surface. An inductance coil was used inside to measure the response. Judgments are made on the elastic and viscous properties of vortices originated in the sample. Particularly, the character of the response signal (amplitude and phase) is explained by irreversible magnetization of the sample, due to vortices' pinning and interaction with surface. Well-calibrated grains used in the ceramic (∼50 μm in average) allowed observation of the ''commensurability'' effect between the pinning centers' and vortex-lattice periods, enhancing the volume force of pinning