Specific Heat in High Magnetic Fields. A Study of the Heavy-Fermion SystemsU(Pt,Pd)3 and CeRu2Si2 and the High-Tc Superconductors ReBa2Cu2O7

摘要

The subject of the thesis is the study of the low-temperature electronic behaviorof two classes of materials: the high-T(c) superconductor YBa2Cu3O7 with rare-earth substitutions for Y, and the heavy-fermion compounds U(Pt,Pd)3 and CeRu2Si2. The thesis is organized as follows: In chapter 2, the experimental technique for performing specific-heat measurements in high static magnetic fields are discussed. In addition, a paper on new possibilities of magnetic ripple shielding for specific heat measurements in hybrid magnets is presented. Chapter 3 is devoted to the high-T(c) superconductors of the series REBa2Cu3O7. In chapter 4, the low-temperature specific heat of REBa2Cu3O7, as studied in magnetic fields up to 5 T, is presented. The authors discuss measurements from which information about the crystal-field level schemes of the rare-earth ions can be derived. Chapter 5 is devoted to specific-heat studies in the heavy-fermion superconductor UPt3, and in the Pd-substituted U(Pt1-xPdx)3 compounds, with x=0.05 and 0.10. Chapter 6 describes the field suppression of the heavy-fermion state in CeRu2Si2.