Non-resonant Microwave Absorption and Boundary Current Response of Ba_0.34K_0.64Fe₂As₂ Superconducting Single Crystals

Boundary current response of Ba_0.34K_0.64Fe₂As₂ (BaK122) single crystals was probed by non-resonant microwave absorption (NRMA) as a function of 100-KHz modulation field at an intermediate temperature, namely, 25 K, which is 10 K below the actual T_c. The measurements were done for both field parallel and perpendicular to the iron arsenide plane configuration. A weak anisotropic effect is noted. However, it is observed that the boundary current response depends on the modulation field value and it increases as we increase the modulation field value from 1 to 9 G. Further, this boundary current response strongly depends on the microwave power. We have shown that these modulation field and microwave power dependence of the boundary current response of NRMA signals in BaK122 iron arsenide crystal can be qualitatively understood through the Dulcic model.