Levitation force between a superconductor and a permanent magnet with cylindrical symmetry

In order to understand the levitation phenomena of superconductors (SCs), experiments are often realized by studying the levitation force between a cylindrical SC and a coaxial permanent magnet. In this work, we study these experiments by theoretical models we have derived in two stages. In the first stage, we assume both that the SC has no demagnetizing effects and that the applied field is vertical in the SC volume. Within these approximations, we derive simple analytical models that can explain the main features of levitation. In a second step, we present a numerical model which simulates the general case, including the effect of demagnetizing fields in the SC and the application of an arbitrary external field that keeps the cylindrical symmetry. The conditions for using either the simplified analytical models or the complete numerical one are discussed. © 2001 Elsevier Science B.V. All rights reserved.