טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentOfer Rinat
SubjectCorrelation between the Critical Temperature of Cuprate
Superconductors and their Magnetic
Interaction
DepartmentDepartment of Physics
Supervisor Professor Amit Keren


Abstract

Previous work in our group demonstrated that for the cuprates superconductors in the underdoped region:  where TC is the superconductor transition temperature, Jf a magnetic energy scale for a given cuprates family, and ns is the superconducting carrier density. However there is still no clear experimental confirmation that Jf is independent of doping for a given family, or of a correlation between the maximum transition temperature Tcmax and the Néel temperature TN.

In the first part of the work I wanted to verify that the energy scale Jf is unique to each family for high temperature superconductors [HTSC], and is constant throughout all the doping range in the family. For this I performed NQR measurements, thus determining doping levels, on YBCO samples with various oxygen contents. I found that TC is proportional to the NQR resonance frequency, and this in tern is proportional to ns. From that   hence Jf must be a constant for the YBCO family.

In the second part of the work I investigated the correlation between TCmax and TN at very low doping, for a given family. For this purpose I used the CLBLCO families of superconductors and applied zero field muon spin relaxation measurements to determine both the spin glass and Néel transition temperatures Tg and TN. This allowed me to construct the phase diagram of the CLBLCO system. Using this phase diagram I showed that the family with the higher value of TN   in the undoped parent compound, and hence a higher value of the magnetic energy scale Jf, has indeed the higher value of  TCmax in the superconducting region.