Observations of Vortex Chains in Bi 2Sr2CaCu2O8+ y by Bitter decoration

M. TOKUNAGA; M. KOBAYASHI; Y. TOKUNAGA; T. TAMEGAI; YANINA FASANO

JOURNAL OF LOW TEMPERATURE PHYSICS

Año: 2003 vol. 131 p. 963 - 967

0022-2291

Vortex states in Bi$_2$Sr$_2$CaCu$_2$O$_{8+y}$ under tilted fields were studied by means of magneto-optical imaging and Bitter decoration. One-dimensional arrangements of pancake vortices (vortex chains) interacting with underlying Josephson vortices are visualized. From the spacing of vortex chains we directly determined the variation of the anisotropy parameter of the electronic mass ($\gamma$) from 800 in slightly underdoped to 180 in highly overdoped samples. These results indicate that the crossing-lattices model for the highly anisotropic superconductors remains relevant at least for $\gamma geq 180$, contrary to what was predicted theoretically by Dogson [Matthew J. W. Dogson, Physica C 369, 182 (2002).]