L.A. Gurevich, I.V. Grigor'eva, N.N.
Kolesnikov, M.P. Kulakov, V.A. Larkin, L.Ya. Vinnikov.
Direct observation of the vortex structure in high-Tc
superconductors in tilted magnetic fields.
A high-resolution Bitter technique has
been used to observe an effect of tilting the external magnetic field on
the flux line lattice (FLL) in Tl2Ba2CaCu2O8+x
single crystals. The FLL was found to remain isotropic , with average vortex
spacing in the FLL corresponding to the normal component of the external
field; no vortex chains or any distortion of the FLL were observed, in
contrast to what the theory predicted. The reason is believed to be that
the formation of the equilibrium vortex state (vortex chains) was prevented
by strong pinning, revealed for our crystals by the M(t) curves.