Magnetic excitations and crystal field splitting study of Co2+ in the triangular lattice antiferromagnets: (Ca,Sr)3CoSb2O9

The Ca3CoSb2O9 and Sr3CoSb2O9 compounds are a model frustrated triangular-lattice compounds. The high frustration on a magnetic lattice may prevent the LRO leads to established QSL ground state. Both of proposed Co2+ compounds does not show any magnetic long-range ordering down to 2 K, however, both triangular-lattice Ca3CoSb2O9 and Sr3CoSb2O9 compounds shows high Curie-temperature of about -76 K and -121 K, respectively suggesting highly frustrated system. Moreover, the Co2+ ions in the distorted octahedral environment are expected to have an effective spin-1/2 due to spin-orbit coupled Karmers doublet ground state. This could be confirmed by measuring the crystal field excitations using an inelastic neutron scattering study at MARI/LTE beamline. The results of the proposed study will provide the direct information of the magnetic excitations which are crucial to understand the true ground state of both of the compounds.