Ac-susceptibility in Oxide Superconductor of Y-system, (II) Single Crystal

Abstract

Magnetic response of YBCO superconductors was investigated in terms of ac-susceptibility including higher-harmonics χn=χn′-i⋅χn″ (n=1, 2, 3, …). Two types of specimens, bulk and thin films of single crystal, were used. χn versus temperature curves observed exhibited peculiar properties to the types of. specimens. The results observed are qualitatively reproduced by the curves calculated on the basis of the Kim-Anderson model for the bulk specimen or the modiflied Bean model for the thin films. This is understood that vortex pinning inside the specimen or surface barrier plays an important rule on the magnetic response for the former or the latter, respectively.