Direct visualization of local pinning forces in Bi2Sr2CaCu2O8+ vortex matter

J. ARAGÓN SÁNCHEZ ; R. CORTÉS-MALDONADO; M. DOLZ; G. RUMI; M. KONCZYKOWSKI; G. NIEVA; P. PEDRAZZINI; Y. FASANO

Simposio; XXIII Simposio Latinoamericano de Física del estado Sólido; 2018

We studied the structural transformations in the surface of the vortex matter nucleated in pristine and electron irradiated Bi2Sr2CaCu2O8+, along the second peak transition by direct observation of individual vortices. The eects of point-like disorder, introduced by irradiation with 2.3 MeV electrons, on the phase diagrams were measured with local Hall probe magnetometry. We observed a signicant depression of: the critical temperature Tc, the rst order phase transition (FOT) and the second peak eld Bsp. In order to visualize the vortex structure with single-vortex resolution we used the magnetic decoration technique. This technique makes possible the analysis of structural transformations induced at the surface in the real space, for images with thousands of vortices in a range of applied elds signicantly broader than other techniques. We analyzed the defect density, Fourier Transform and the structure factor of the nucleated vortex matter for elds near to Bsp. Structural features related to an amorphous or polycrystalline state are not observed at elds above Bsp. This result is in agreement and complements small angle neutron scattering measurements for this material [1].[1] Pautrat, A. et al. Phys. Rev. B, 75, 224512 (2007).