A Study on the Microwave Response of M gB2 Superconducting Thin Films
SHI Libina,b , WANG Yunfeia , ZHANG Chena , ZHANG Guohuaa , LUO Sheng a , ZHANG Xueqiangc ,
LI Chunguangc , LI Hongc , YU Zengqiangd, WANG Furend , and HE Yushengc
a
b
c
d
Department of Physics, University of Science and Technology Beijing , Beijing 100083, China
Department of Physics , Bohai University, Liaoning Jinzhou 121000 ,China
Institute of Physics, Chinese Academy of Sciences , Beijing 100080, China
School of Physics, Peking University , Beijing 100871, China
M gB2 superconducting thin films were prepared by pulsed laser deposition (P LD) from a superconducting M gB2 target on 10×10 mm sapphire (001) substrates with post annealing in Ar atmosphere.
The transition temperature TC is around 35K with transition width less than 1K. The critical current
density measured at 4.2K and zero field is about 106 A/cm2 . Microwave response of the films was studied
systematically by coplanar resonator technique. In addition, microstrip resonator, of which thin gold film
was used as the ground plane, was also used for comparison. Temperature and power dependent surface
impedance of the films were measured and the parameter γ (γ =∆RS /∆XS ), which is independent of resonator geometrical factor, was used to analyze their intrinsic properties. Consistent results were obtained
from two different type resonators and indicate clearly the s-wave nature of the order parameter. The
results were also discussed under the light of the anisotropic one-gap and the isotropic two-gap models.
At high microwave power, results show a characteristic signature associated with weak links, which were
also compared with AF M studies.
Sorting category: Bb Superconductivity
Keywords: M gB2 , film , microwave response
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