ACTA

Microwave Characterization of 122-Pnictides by a Superconducting Niobium Cavity

P. Gierłowski^a, B.C. Camargo^a, K. Cho^b, I. Abaloszewa^a, A. Abaloszew^a, M. Jaworski^a
^aInstitute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warszawa, Poland
^bAmes Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

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We present first results of our microwave measurements of Ba_1-xK_xFe₂As₂ (with x=0.34) single-crystal pnictide, using a cylindrical superconducting niobium microwave cavity, working at approximately 26.2 GHz in the TE₀₁₁-mode. The measured samples, after initial magneto-optic tests of their uniformity, are cut and glued on a sapphire rod, whose temperature can be independently controlled between 5 K and 40 K. Microwave measurements are performed by a vector network analyzer in the reflection mode, i.e. the S₁₁ component of the complex scattering matrix S is measured. The loaded quality factor Q_Ls and the shift of the resonance position are measured during a temperature sweep, followed by calculating of the unloaded quality factor Q_0s and the resonance frequencies f_Ls and f_0s by means of the Kajfez procedure where the subscript ``s'' denotes the sample. The values of the superconducting penetration depth change δλ_L and of the surface resistance R_s are calculated approximating the single crystal sample by a flat cylindrical disk of appropriate size, based on a procedure described by Maier and Slater.

DOI:10.12693/APhysPolA.135.47
PACS numbers: 07.57.Pt, 74.25.N-, 74.70.Xa