On the origin of the irreversibility line in thin YBaCuO7 films with and without columnar defects
R. Prozorov, M. Konczykowski, B. Schmidt, Y. Yeshurun, A. Shaulov, C. Villard, G. Koren
Abstract
We report on measurements of the angular dependence of the irreversibility temperature
T
irr
(θ)
in
YB
a
2
C
u
3
O
7−δ
thin films, defined by the onset of a third harmonic signal and measured by a miniature Hall probe. From the functional form of
T
irr
(θ)
we conclude that the origin of the irreversibility line in unirradiated films is a dynamic crossover from an unpinned to a pinned vortex liquid. In irradiated films the irreversibility temperature is determined by the trapping angle.