Specific Features of the Nonlinear Microwave Response of the (Na{sub 0.3}K{sub 0.7}){sub x}Fe{sub 2 –} {sub y}Se{sub 2} Sodium–Potassium Ferroselenide-Based Multiband Superconductors
Abstract—Temperature dependences of the third-harmonic power for the (Na{sub 0.3}K{sub 0.7}){sub x}Fe{sub 2 –} {sub y}Se{sub 2} sodium–potassium ferroselenide single crystals have been investigated by nonlinear near-field microwave microscopy. The temperature dependence of magnetic susceptibility at a frequency of 100 kHz for this compound has been measured. The experimental results suggest a double-gap structure of the (Na{sub 0.3}K{sub 0.7}){sub x}Fe{sub 2 –} {sub y}Se{sub 2} superconductor.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗