Imaging of vortex matter in Fe-Se su- perconductors using the Bitter decoration technique

M. L. AMIGÓ; R. CORTÉS-MALDONADO; G. NIEVA; Y. FASANO

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

We were able to image single vortex position in superconducting b-FeSe and FeSe0;95S0;05 single crystals, by means of the Bitter decoration technique. Several structural properties of the vortex array were depicted in this samples at characteristic magnetic fields applied up to 5 Oe parallel to the c- crystallographic axis of the platelet shaped crystals. In -FeSe crystals,a disordered square symmetry is observed with one of the compact planes oriented along the sample edge at 45 of the a-crystallographic axis. Towards the center of the sample, the lattice becomes more and more disordered and this orientation weakens. In FeSe0;95S0;05, lines with higher vortex density indicatethe presence of twin-boundaries between orthorhombic domains with different orientations. The presence of twin boundaries seems to induce regions of squarelike vortex structure.