Surface impedance in the antiferromagnetic and superconducting states of underdoped BaFe1.93Ni0.07As2 crystals

• Surface impedance measurements of superconducting underdoped BaFe1.93Ni0.07As2 crystals.
• Real R and imaginary X parts of the surface impedance differ from each other in the antiferromagnetic state.
• Effective conductivity in the superconducting state is extracted.

Measurements of the real R and imaginary X parts of the surface impedance were performed in underdoped BaFe1.93Ni0.07 As2 crystals in the frequency range 10 MHz–1.5 GHz. The establishment of the antiferromagnetic order at TN~50 K gives rise to anomalous increase of electron scattering time. Drude type conductivity yields X and R differ from each other. The increase of the real conductivity σ1 in the superconducting state is attributed to a rapid decrease of the quasiparticle scattering time. This result gives evidence of coexistence of superconductivity and antiferromagnetism.