Anisotropy dependence of vortex states under tilted-fields studied by Bitter decorations

Bitter decorations of vortex states under tilted-fields in YBa2Cu3O7−δ and YBa2(Cu1−xAlx)3O7−δ with x = 0.04 are reported. To study effects of the anisotropy parameter on vortex states in tilted-fields, we prepared samples with various doping levels controlled by oxygen annealing. The chain + lattice arrangements that are characteristic of the crossing-lattices states were observed in underdoped samples. In these samples, the observed spacing between chains systematically depends on the magnitude of in-plane field.