oral: Ordered- disorder transition in vortex systems throughout the Peak effect

G. PASQUINI; D. PÉREZ DAROCA; C. CHILIOTTE; G. LOZANO; V. BEKERIS

Iguazú

Simposio; XIX Latin American Symposium of Solid State Physics (SLAFES2008); 2008

Vortex lattice (VL) in type II superconductors may be considered as a modelcomplex system where competing interactions give rise to a complex phasediagram. In this context the VL undergoes an order-disorder transition thatoriginates the anomaly known as Peak Effect (PE). The underlying physics ofthis transition and the stability of ordered and disordered domainsthroughout the PE are issues that remain unsolved. As a common fact, astrong metastability masks the stationary VL configurations (VLCs) in lowand high Tc materials. In this work, we explore the VLC landscape at eachtemperature (field) by applying different shaking protocols beforemeasurements. By means of linear ac susceptibility experiments, that avoidVL reorganization, we explore quasi-static stable and metastable VLCs. Weshow results obtained in $NbSe_{2}$ and $YBa_{2}Cu_{3}O_{7-y}$ singlecrystals that indicate that a different physics governs the PE phenomena inboth cases. We focus in $NbSe_{2}$ system, where we are able to access tostationary configurations. We identify three different regions: for $%T<T_{1}(H)$, stable VLCs are maximally ordered and for $T>T_{2}(H)$configurations are fully disordered. In the $T_{1}<T<T_{2}$ region we findtemperature dependent stable configurations with intermediate degree ofdisorder, indicating a coexistence of ordered and disordered domains.