Microwave electrodynamics of the antiferromagnetic superconductor GdBa2Cu3O7−δ
The temperature dependence of the microwave surface impedance and conductivity are used to study the pairing symmetry and properties of cuprate superconductors. However, the superconducting properties can be hidden by the effects of paramagnetism and antiferromagnetic long-range order in the cuprates. To address this issue we have investigated the microwave electrodynamics of GdBa_2Cu_3O_{7-\delta}, a rare-earth cuprate superconductor which shows long-range ordered antiferromagnetism below T_N=2.2 K, the Neel temperature of the Gd ion subsystem. We measured the temperature dependence of the surface resistance and surface reactance of c-axis oriented epitaxial thin films at 10.4, 14.7 and 17…
Microwave surface impedance of proximity-coupled superconducting (Nb)/spin-glass (CuMn) bilayers
The surface impedance of Nb/CuMn (superconducting/spin-glass) bilayers has been measured at 10 GHz with the parallel plate resonator technique to obtain information about the exotic behavior of the order parameter in superconducting/magnetic proximity systems. The data strongly differs from the superconducting/normal-metal case, showing the magnetic nature of the CuMn layer, which acts as a weak ferromagnet. The results are described in the framework of two models for the electrodynamics of superconducting/ferromagnetic (S/M) bilayers characterized by a proximity-coupling length scale which is independent of temperature.