Static and dynamic order-disorder transitions of the vortex lattice in YBa2Cu3O7-d crystals: the effect of point defects, anisotropy, temperature and magnetic field
National Science Center "Kharkov Institute of Physics and Technology", Akhiezer Institute for Theoretical Physics 1 Akademicheskaya Str., Kharkov 61108, Ukraine
Received August 10, 2009, revised September 22, 2009
The experimental data on field Fp (H) and
angular Fp(α) dependences of pinning force in the YBa2Cu3O7–δ crystal with different concentrations of point defects are reported. Comparison of the Fp(H) and Fp (α) dependences gives strong arguments to suggest that minimum in the Fp (α) dependence measured at low vortex velocity u corresponds to the order–disorder transition of the vortex lattice (VL). It is also shown that high velocities result in shifting the minimum towards higher values of angle α, due to a partial dynamic ordering of the disordered VL.