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Title: Influence of hole content and controlled disorder on the magnetic susceptibility, isotope exponents and resistivity of high-Tc cuprates
Author: Islam, R. S.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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The uniform magnetic susceptibility of La2-xSrxCu1-yZnyO4 has been investigated over a wide range of impurity (Zn) concentration for different planar carrier (hole) content, p (º x, for this system), extending from underdoped to heavily overdoped regions. A doping dependent Zn-induced magnetic behaviour is observed for these compounds. The apparent Zn induced moment (expressed as peff2/Zn in units of mB2) is larger in the underdoped side and, decreases quite sharply around p ~ 0.19,without much change for further overdoping. This indicates a possible role of the pseudogap on the Zn induced magnetic behaviour, as there are indications that the pseudogap is present only for p £ 0.19. It is shown that the data can also be interpreted in terms of a Zn-induced low energy quasiparticle resonance that depends on the presence of the pseudogap. The oxygen isotope exponents in superconducting transition temperature and superfluid density, a(Tc) and aps), respectively, have been studied as a function of hole (x) and impurity (y) contents in La2-xSrxCu1-yZnyO4. The isotope exponents displayed a canonical relationship, except around the region of x ~ 1/8. The results are discussed in terms of the presence of the pseudogap and the stripe correlations. In-plane resistivity measurements under applied magnetic fields (up to 12 Tesla), pab(T,H), have been carried out on c-axis oriented thin films of Y0.95Ca0.05Ba2(Cu1-yZny)3O7-d with varying amount of in-plane disorder (Zn) and hole concentration. Following an earlier work on sintered compounds of the same system, we have obtained supplementary information about the characteristic pseudogap temperature, T*(p), from the analysis of the pab(T,H) data. Our thin film data support the earlier findings that T*(p) falls below Tc0(p) (º Tc(p) for pure compound) in the overdoped side and, extrapolates to zero at p ~ 0.19.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available