The role of disorder in superconducting magnesium diboride MgB2 policrystalline films is investigated in the high frequency range by a coplanar microwave resonator technique. Two sources of disorder are considered, heavy-ion irradiation damage and sample ageing. Microwave measurements are analyzed in the framework of the two-gap model with strong interband scattering contribution. It turns out that disorder enhancement increases the interband scattering rate, resulting in a reduction of the surface resistance at low temperatures, due to a slight increase of the gap. Moreover, increasing disorder at grain boundaries induces a nonmonotonic residual surface resistance, showing the features of a resistive behavior for the highest disorder level. Finally, the effects of the different kinds of disorder on the intrinsic and on the grain-boundary properties of the MgB2 films are compared and discussed.

Effects of disorder on the microwave properties of MgB2 polycrystalline films / Ghigo, Gianluca; Ummarino, Giovanni; Gerbaldo, Roberto; Gozzelino, Laura; Laviano, Francesco; Mezzetti, Enrica. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 74:(2006), pp. 184518-1-184518-6. [10.1103/PhysRevB.74.184518]

Effects of disorder on the microwave properties of MgB2 polycrystalline films

GHIGO, GIANLUCA;UMMARINO, Giovanni;GERBALDO, Roberto;GOZZELINO, LAURA;LAVIANO, FRANCESCO;MEZZETTI, Enrica
2006

Abstract

The role of disorder in superconducting magnesium diboride MgB2 policrystalline films is investigated in the high frequency range by a coplanar microwave resonator technique. Two sources of disorder are considered, heavy-ion irradiation damage and sample ageing. Microwave measurements are analyzed in the framework of the two-gap model with strong interband scattering contribution. It turns out that disorder enhancement increases the interband scattering rate, resulting in a reduction of the surface resistance at low temperatures, due to a slight increase of the gap. Moreover, increasing disorder at grain boundaries induces a nonmonotonic residual surface resistance, showing the features of a resistive behavior for the highest disorder level. Finally, the effects of the different kinds of disorder on the intrinsic and on the grain-boundary properties of the MgB2 films are compared and discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/1433183
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