Direct visualization of the order-disorder transition in vortex matter in Bi2Sr2CaCu2O8+

JAZMÍN ARAGÓN SÁNCHEZ; RAÚL CORTÉS MALDONADO; MOIRA INÉS DOLZ; GONZALO RUMI; M. KONCZYKOWSKI; G. NIEVA; P. PEDRAZZINI; Y. FASANO

Bariloche

Conferencia; Poster presentado en el XXIII Latin American Symposium on Solid State Physics; 2018

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