Effect of Different Thickness Crystalline SiC-Buffer Layers on Superconducting Properties and Flux Pinning Mechanism of ${rm MgB}_{2}$ Films

摘要

We have fabricated the superconducting ${rm MgB}_{2}$ films grown on three different crystalline SiC-buffer layers of different thickness by means of the hybrid physical–chemical vapor deposition technique and pulsed laser deposition method. Significant changes in the microstructural and superconducting properties of ${rm MgB}_{2}$ films with addition of crystalline SiC-buffer layers were observed. The microstructural analyses of ${rm MgB}_{2}$ films revealed that columnar grains were formed perpendicularly to the substrates, thus, enhancing all critical current density values at 5 and 20 K for all SiC-buffered- ${rm MgB}_{2}$ films. The scaling behavior of the flux pinning force shows a magnetic field-dependent feature with different pinning mechanisms, from which one can infer that there are additional pinning centers that exist in the samples and cannot be interpreted by a simple superposition of different types of elementary pinning sources.