Unusual magnetic order and crystalline electric fields in itinerant Cerium-based materials

Magnetic frustration can generate new quantum phases of matter with exotic physical properties. Lanthanide-based materials can generate frustration from the geometrical arrangement of magnetic ions, magnetocrystalline anisotropy from spin-orbit coupling (SOC) and crystalline electric field (CEF) effects, Kondo interactions, and conduction electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic exchange interactions. Here, we report investigations of two Ce-based materials, CeLiBi₂ and CeLi₃Bi₂, with frustrated magnetic ground states. In tetragonal CeLiBi₂, a complex competition between CEF anisotropy and extended magnetic exchange leads to a multitude of intertwined quantum phases. This includes hard-axis metamagnetism, highly mobile carriers, incommensurate cycloidal magnetic order below 3.4 K in neutron diffraction data, and quantum oscillations in dilatometry and resistivity measurements. Neutron diffraction and NMR measurements reveal itinerant triangular lattice CeLi₃Bi₂ exhibits stripy antiferromagnetic order below 1.2 K with small Ce moment magnitudes. In CeLi₃Bi₂, we further investigate the splitting of the local Ce ion D_3d CEF utilizing combined magnetic susceptibility, specific heat, and magnetospectroscopy measurements.