Eur. Phys. J. B 51, 537-542 (2006)
https://doi.org/10.1140/epjb/e2006-00260-4

Near-T_c second-harmonic emission in high-density bulk MgB₂ at microwave frequency

¹ CNISM and Dipartimento di Scienze Fisiche e Astronomiche, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy
² EDISON S.p.A., Divisione Ricerca & Sviluppo, Foro Buonaparte 31, 20121 Milano, Italy

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

Received: 11 April 2006
Revised: 25 May 2006
Published online: 28 June 2006

Abstract

We discuss the microwave second-harmonic generation in high-density bulk MgB₂, prepared by the reactive liquid Mg infiltration technology. The intensity of the harmonic signal has been investigated as a function of temperature and amplitudes of the DC and microwave magnetic fields. The results are discussed in the framework of a phenomenological theory, based on the two-fluid model, which assumes that both the microwave and static magnetic fields, penetrating in the surface layers of the sample, weakly perturb the partial concentrations of the normal and superconducting fluids. We show that, in order to account for the experimental results, it is essential to suppose that in MgB₂ the densities of the normal and condensed fluids linearly depend on the temperature.