Crystalline electric field excitations in frustrated antiferromagnets YbCuS2 and YbAgSe2 with an effective spin-1/2 zigzag chain

In rare-earth based semiconductors and insulators, superexchange interaction mediated by nonmagnetic anions plays the role in ordering of localized 4f moments. A zigzag spin chain is one of the appropriate stages to study the magnetic frustration relevant to a quantum spin liquid. In the present work, we focus on an Yb-based semiconductors YbCuS2 and YbAgSe2 with an effective spin-1/2 zigzag chain. The aim of the present experiment is to understand the origin of the 1/3 magnetization plateau and the magnetic frustration effect through investigation of the crystalline electric field (CEF) level schemes and the single-ion magnetic anisotropy. To determine the CEF schemes, we plan to perform inelastic neutron scattering (INS) experiments using powdered samples. Here, a wide energy range of MARI is essential because the large energy scale is expected in these compounds. The CEF level schemes will be determined by analyzing the temperature and Q dependences of the intensity of the excitation peaks.