Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB$_2$ samples

Yu. A. Nefyodov; M. R. Trunin; A. F. Shevchun; D. V. Shovkun; N. N. Kolesnikov; M. P. Kulakov; A. Agliolo Gallitto; S. Fricano

doi:10.1209/epl/i2002-00656-8

paper

Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB $_{2}$ samples

arXiv:cond-mat/0107057 · doi:10.1209/epl/i2002-00656-8

Abstract

The real $R_{s} (T)$ and imaginary $X_{s} (T)$ parts of the surface impedance $Z_{s} (T) = R_{s} (T) + i X_{s} (T)$ in polycrystalline MgB $_{2}$ samples of different density with the critical temperature $T_{c} \approx 38$ K are measured at the frequency of 9.4 GHz and in the temperature range $5 \leq T < 200$ K. The normal skin-effect condition $R_{s} (T) = X_{s} (T)$ at $T \geq T_{c}$ holds only for the samples of the highest density with roughness sizes not more than 0.1 $μ$ m. For such samples extrapolation $T \to 0$ of the linear at $T < T_{c} /2$ temperature dependences $λ_{L} (T) = X_{s} (T) / ω μ_{0}$ and $R_{s} (T)$ results in values of the London penetration depth $λ_{L} (0) \approx 600$ Åand residual surface resistance $R_{r es} \approx 0.8$ m $Ω$ . In the entire temperature range the dependences $R_{s} (T)$ and $X_{s} (T)$ are well described by the modified two-fluid model.

7 pages, 3 figures. Europhysics Letters, accepted for publication

Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB $_{2}$ samples

Abstract

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Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB2​ samples

Abstract

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Characteristic features of the temperature dependence of the surface impedance in polycrystalline MgB $_{2}$ samples