Synthesis and characterization of single crystals of rare-earth containing magnetic topological semimetal candidates

Abstract

In this thesis, I report the synthesis and study of various rare-earth containing magnetic topological semimetal candidates, namely CeBi, EuCd2As2, and EuIn2. CeBi forms a part of the larger family of rare-earth monopnictides, hosting myriad topological properties across the family. We report a systematic study of the magnetic and transport properties with varying temperatures and applied magnetic fields in CeBi, and study the evolution of magnetoresistance behavior in different temperature and field regimes. In EuCd2As2, we study the evolution of magnetism with chemical substitution. We report the synthesis and characterization of Eu(Cd1−xAgx)2As2 and Eu1−yNayCd2As2 and construct temperature-substitution phase diagrams. We further show that a magnetic state with a net ferromagnetic moment is stabilized by both Ag and Na doping. EuIn2, yet another Eu-containing magnetic topological semimetal candidate, was synthesized and three successive magnetic transitions were observed at low temperatures. Furthermore, M ̈ossbauer spectroscopy measurements suggest an incommensurate moment modulated phase setting in at the highest temperature magnetic transition, eventually evolving into a non-modulated yet incommensurate phase below the lowest transition. Finally, we briefly look at the search for single ion Kondo effect in the rare-earth monopnictide series, with Ce doping in ScSb and LaSb.