Eur. Phys. J. B 53, 315-322 (2006)
https://doi.org/10.1140/epjb/e2006-00381-8

Magnetic hysteresis in the microwave surface resistance of Nb samples in the critical state

CNISM and Dipartimento di Scienze Fisiche e Astronomiche, Universita di Palermo, Via Archirafi 36, 90123 Palermo, Italy

Corresponding author: ^a agliolo@fisica.unipa.it

Received: 28 July 2006
Revised: 15 September 2006
Published online: 18 October 2006

Abstract

We discuss the hysteretic behavior of the field-induced variations of the microwave surface resistance in superconductors in the critical state. Measurements have been performed in a bulk sample of Nb and a powdered one at different values of the temperature. We discuss a model, based on the Coffey and Clem theory, in which we take into account the flux distribution inside the sample, due to the critical state. The experimental results are quite well justified in the framework of our model. We show that by fitting the experimental data it is possible to determine the value of the critical current density and its field dependence.