Magnetic, thermodynamic and transport properties of the magnetic semiconductor Fe₁₋xCoxS₂ and superconducting LaSb₂

In recent years magnetic semiconductors have attracted a great deal of attention because it is thought that they can be used to generate spin polarized current in spintronics, an emerging field where the spin degree of freedom of charge carriers is utilized in microelectronic devices. In this dissertation work, we investigate the magnetic, thermodynamic, and transport properties of the magnetic semiconductor Fe_1-XCo_xS₂ for x less than 0.14, the doping range where Insulator-to-Metal and paramagnetic-to-ferromagnetic transitions occur. We discovered that the Kondo effect is an important ingredient in the paramagnetic region of magnetic semiconductor Fe_1-XCo_xS₂. Disorder that comes with doping, coupled with the Kondo effect and the RKKY interaction between the local moments, leads to the observed features of spin clusters and the Griffiths phase. This inhomogeneous magnetic state can be used to explain the resulting physical properties, including the NFL behavior as evidenced by the increase of C/T at very low temperature in proximity to the zero-T critical point. A second system, LaSb₂, is found to have a very inhomogeneous superconducting transition at low temperatures. We have discovered that the application of pressure induces a much more homogeneous superconducting ground state in this highly layered compound.

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physical Sciences and Mathematics

Grantor

Physics and Astronomy

Year dc:date.available

2006

Author dc:creator

• Guo, Song

• non-fermi-liquid
• kondo effect
• magnetic semiconductor
• griffiths phase
• superconducting

Statement dc:rights

• unrestricted
• Release the entire work immediately for access worldwide.

Identifier

etd-07132006-124901
https://repository.lsu.edu/gradschool_dissertations/1433

OAI identifier oai:identifier

oai:repository.lsu.edu:gradschool_dissertations-2432