Surface impedance of BaFe2-xNixAs2 in the radio frequency range

We report measurements of the temperature dependence of the surface impedance in superconducting BaFe1.93Ni0.07As2 crystals using the radiofrequency reflection technique in the 52-xNixAs2 has attracted much interest. For a Ni doping level of 7% the superconducting phase transition is found around 20K. The temperature dependence of the superconducting penetration depth was determined.