Eur. Phys. J. B 45, 47-53 (2005)
https://doi.org/10.1140/epjb/e2005-00163-x

Surface-barrier effects in the microwave second-harmonic response of superconductors in the mixed state

¹ INFM and Dipartimento di Scienze Fisiche ed Astronomiche, Universita di Palermo, Via Archirafi 36, 90123 Palermo, Italy
² EDISON S.p.A. - Divisione Ricerca e Sviluppo, Via U. Bassi 2, 20159 Milano, Italy

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

Received: 11 November 2004
Revised: 25 February 2005
Published online: 16 June 2005

Abstract

We report on transient effects in the microwave second-harmonic response of different type of superconductors in the mixed state. The samples have contemporarily been exposed to a dc magnetic field, varying with a constant rate of 60 Oe/s, and a pulsed microwave magnetic field. The time evolution of the signal radiated at the second-harmonic frequency of the driving field has been measured for about 500 s from the instant in which the dc-field sweep has been stopped, with sampling time of ~0.3 s. We show that the second-harmonic signal exhibits two relaxation regimes; an initial exponential decay, which endures roughly 10 s, and a logarithmic decay in the time scale of minutes. Evidence is given that the decay in the time scale of minutes is ruled by magnetic relaxation over the surface barrier.