טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGil Drachuck
Subject2D Superconductivity in La2-xSrxCuO4 Single Crystals
DepartmentDepartment of Physics
Supervisor Full Professor Keren Amit
Full Thesis textFull thesis text - English Version


Abstract

We report direction dependent magnetization measurements in LaxSr2-xCuO4 single crystals. The crystals were grown using traveling solvent floating zone method and were cut into rectangular needle-like shapes with the "c" direction parallel or perpendicular to the needle symmetry axis. The magnetic anisotropies were studied in details near the critical temperatures using a SQUID magnetometer. The measurements were done in the zero field limit using magnetic field H < 1 Oe, which was found lower than the critical field Hc1 at T -> Tc. A difference in Tc of 0.65 K was observed between parallel and perpendicular direction of the optimally doped samples (x=0.15). Higher anisotropies in Tc of 2.6 K and 4.5 K were observed in under doped samples, with x=0.08 and x=0.07 Sr doping respectively. We confirmed that the effect is not caused by sample inhomogeneity, needle dimensions, cooling rates, critical fields and vortex penetration, misalignment, etc. Although a two dimensional phase transitions is theoretically forbidden, recent theoretical and experimental efforts reported of such a phase transition in layered superconductors. Our results indicate that there is a temperature region at which LaxSr2-xCuO4 exhibits two-dimensional superconductivity from a Meissner effect point of view.