Lower boundary field of the triangular lattice phase in Josephson vortices

摘要

The Josephson-vortex flow resistance oscillates as a function of magnetic field when a triangular vortex lattice is formed. In order to study the lower boundary field of the triangular-lattice phase of Josephson vortex, the vortex-flow resistance as a function of magnetic field parallel to the ab-plane was measured over a wide range of temperatures on a Bi2Sr2CaCu2O8+y (Bi-2212) single crystal whose oxygen content was controlled by annealing in vacuum. We have found that the starting field H-start of the oscillations, which corresponds to the boundary field of the triangular-lattice phase, decreases systematically with increasing anisotropy parameter (gamma) of Bi-2212 at all measured temperatures. This behavior is consistent with various theoretical expectations that the boundary field is inversely proportional to gamma. (C) 2004 Published by Elsevier B.V.