Thesis (Ph. D.)--University of California, San Diego, 1983. / Vita. Includes bibliographical references (leaves 156-159).

Thesis (Ph. D.)--University of California, San Diego, 1983. / Vita. Bibliography: leaves 156-159.

No description available.

No description available.

PrOs₄Sb₁₂ is the first known heavy fermion superconductor containing Pr. Many experiments show results indicating unconventional superconductivity in this system. Most notably, PrOs₄Sb₁₂ exhibits two superconducting transitions. The upper transition occurs at Tc₁ ≈ 1.89 K and the lower transition occurs at Tc₂ ≈ 1.72 K. There are many features of this system that are not understood and do not have a unifi ed consensus among researchers. Many issues remain unanswered, such as the origin of superconductivity, symmetry of the superconducting energy gap, and the nature of the two superconducting transitions. We present specific heat data for a single PrOs₄Sb₁₂ crystal. The data show two superconducting transitions. Variance in the lower superconducting transition (among various samples) suggests multiple superconducting phases. Power law dependence of the low temperature specific heat is indicative of asymmetric energy gap. Cuprates are unconventional high temperature superconductors. The theory on origin and characteristics of superconductivity in these systems is still a debated issue. Experiments indicate presence of a phase in these systems that occurs above the superconducting transition temperature which exhibits some common characteristics with the superconducting state. An important issue is the nature of this so-called "pseudogap" phase and its relationship to the superconducting state. We have developed an experimental apparatus and procedure for measuring the specific heat of a high temperature superconductor and demonstrated it by measuring the heat capacity of a YBCO high-Tc superconductor sample.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Oxygen hole-doping effects on a spin-chain system, Ca[subscript 2+chi]Y[2-chi]Cu₅O[subscript 10-delta](CaYCuO) are reported. CaYCuO is a good specimen to study the magnetic properties of the CuO₂ chain at the ground state because it has no complex structure other than the chain and it has hole dopability up to the formal copper valence number of +2.4. Specifically, we can dope holes into the CuO₂ chain by substituting Ca²⁺ for Y³⁺ or by utilizing oxygen deficiency. After a systematic study of the two methods to dope holes, we found that oxygen doping makes a more critical change in magnetic ordering in the chain than the replacement of Ca²⁺. Oxygen deficiency effects of the chain on the magnetic properties were explained using a mean field theory. A new relation for the effective hole doping was found as p = x - [alpha delta], where a = 3/2(x - [delta]) - 1/4. We study the anisotropy of magnetic properties of single crystal Li-cathode material (LiFePO₄) for g-factor, Curie-Weiss temperature, and effective moment. Magnetic properties Au/SiO₂ coated [gamma]-Fe₂O₃ are compared with pure [gamma]-Fe₂O₃ finding a decrease in the blocking temperature and the irreversible temperature for the coated nanoparticles. / text

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