Microwave absorption in carbon-doped YNi4B superconductors Original Research Article

Comparative microwave and magnetometric studies of YNi4B and YNi4BC0.2 weak superconductors are presented. In both compounds, microwave absorption signals, typical for highly granular superconductors, were found. The intriguing phenomenon was the narrow temperature range 5–6 K in which strong superconducting fluctuations occurred in the clusters formed by touching grains, or possibly, inside individual fine grains. The granular-like behaviour of YNiB-family superconductors can be ascribed to inclusions of a carbon-rich superconducting phase, probably YNi2B2C, dispersed in a YNi4B normal metal host. The hypothesis was supported by AC susceptibility and DC magnetisation measurements, which revealed a low content of superconducting phase in the YNi4B-family compounds.