Studies of inhomogeneity effects on properties of superconducting materials

Author(s)

Luís Augusto Gomes Báring

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2008-04-14

Examining board members

Iakov Veniaminovitch Kopelevitch; Renato de Figueiredo Jardim; Pascoal José Giglio Pagliuso

• Advisor: Iakov Veniaminovitch Kopelevitch

Abstract

In this work we study the physical properties of bismuth samples. Crystalline bulk bismuth, in the rhombohedral phase, is not superconducting, but, in the cubic phase, for example (obtained under pressure), in films and in the amorphous phase, may present superconducting transition. We observed superconductivity in a bismuth virgin powder and in samples prepared upon annealing this powder. Due to the small volumetric superconducting fraction we suspect that the superconductivity is related to the sample's surface. Moreover, the superconducting properties are strongly dependent upon the annealing conditions (these samples may be either superconducting or not). We also performed magnetotransport measurements in a single-crystalline bismuth sample and observed a characteristic feature of this material, namely, metal-insulator transition driven by applied magnetic field (AU)