1999/01/11 by R. Grosser, Grosser, R., P. Hoecherl +8
Engineering · Physics and Astronomy · #Characterization and Applications of Magnetic Nanoparticles #FOS: Physical sciences #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #Superconductivity (cond-mat.supr-con) #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/9901085
9 pages, 12 figures
arxiv created 1999/01/11 · openalex publication_date 1999/01/11 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The damping of the oscillations of a small permanent magnet (spherical shape, radius 0.1 mm) levitating between two parallel YBCO surfaces is measured as a function of oscillation amplitude and temperature. The losses in the samples (epitaxial thin films, bulk granular and bulk melt-textured) are analyzed in terms of oscillating shielding currents flowing through trapped flux lines whose motion gives rise to electric fields. We find dissipation to originate from different mechanisms of flux dynamics. At small amplitudes there is a linear regime described by a surface resistance varying from 10-9 Ohm for bulk samples down to 10-13 Ohm for the thin films at low temperatures. With increasing amplitude various nonlinear regimes are observed, firstly collective pinning with diverging energy barriers, secondly in bulk samples above 85 K hysteretic damping, and finally in thin films exponentially large losses which can be described by pinning energies vanishing linearly at large currents.