Crystal Symmetry and Physical Properties of Selected Intermetallic Compounds

Author

Joanna Blawat, Louisiana State University and Agricultural and Mechanical CollegeFollow

Degree

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

Document Type

Dissertation

Abstract

Intermetallic compounds exhibit various interesting phenomena, such us superconductivity and non - trivial topology, which are usually dictated by the interplay of crystal symmetry, spin - orbit coupling, electron – electron and electron – phonon interactions. This dissertation presents the experimental study of interesting phenomena observed in Pd - P – based, and Eu - based compounds due to the interplay between various degrees of freedom.

For Pd-P-based compounds, we find that CaPd₂P₂ and SrPd₂P₂ crystallize in a tetragonal space group I4/mmm and exhibit superconductivity below Tc = 1.0 K and 0.7 K, respectively. The antibonding interaction between Pd and P orbitals play a critical role in inducing superconductivity. On the other hand, CaPd_1-xP_1+x and SrPd_1-xP_1+x form a honeycomb lattice: one is centrosymmetric and another non-centrosymmetric, respectively. Our study indicates that it is necessary to mix Pd and P site within honeycomb lattice to stabilize the crystal structure. Both compounds are diamagnetic materials and exhibit metallic behavior.

For Eu-based compounds, involving f – electrons, magnetism will play an important role. We discovered a new magnetic semiconductor Eu₃Sn₂P₄, which shows an antiferromagnetic transition at T_N = 14 K, and semiconducting behavior with the energy gap of 0.14 eV. Eu can also bring the magnetism into the topologically non-trivial materials, which motivated us to study EuZn₂As₂, an analogue to EuCd₂As₂. EuZn₂As₂ exhibits an A - type antiferromagnetic ordering below T_N = 19 K, with strong ferromagnetic fluctuations up to T_fl ~ 200 K. Since the T_N and T_fl are two times higher than that for EuCd₂As₂, it provides a better platform for exploring topological properties in both the magnetically ordered and fluctuation regimes. The high magnetic field resistivity data show giant magnetoresistance (MR) unsaturated up to 60 T and Shubnikov-de Haas quantum oscillations with a single frequency of F = 38 T. Quantitative data analysis indicates that the corresponding hole band has a non - trivial Berry phase and reaches the first Landau level at ~50 T, thus exhibiting linear MR in the quantum limit.

Date

4-11-2023

Recommended Citation

Blawat, Joanna, "Crystal Symmetry and Physical Properties of Selected Intermetallic Compounds" (2023). LSU Doctoral Dissertations. 6088.
https://repository.lsu.edu/gradschool_dissertations/6088

Committee Chair

Jin, Rongying

DOI

10.31390/gradschool_dissertations.6088