Chemical Pressure Tuning Magnetism from Pyrochlore to Triangular Lattices

Geometrically frustrated lattices combined with magnetism usually host quantum fluctuations that suppress magnetic orders and generate highly entangled ground states. Three-dimensionally (3D) frustrated magnets generally exist in the diamond and pyrochlore lattices, while two-dimensionally (2D) frustrated geometries contain Kagomé, triangular, and honeycomb lattices. In this work, we reported using chemical pressure to tune the magnetism of the pyrochlore lattice in LiYbSe₂ into a triangular lattice by doping Ga or In. Li_3-GaYb₃Se₆ and Li_3-InYb_3-InSe₆/Li_3-InYb_3-□Se₆ crystallize in a trigonal α-NaFeO₂ structure-type (space group R3̅m) and can be synthesized using either LiCl or Se flux. In Li_3-GaYb₃Se₆, Ga³⁺ and Li⁺ are mixed, leaving Yb³⁺ on the triangular plane. Instead of just Li⁺ being replaced in Li_3-GaYb₃Se₆, In³⁺ was observed in both the Li⁺ and Yb³⁺ layers in Li_3-InYb_3-InSe₆ depending on the reaction conditions. Dominant antiferromagnetic interactions are revealed by magnetic measurements in both Li_3-GaYb₃Se₆ and Li_3-InYb_3-InSe₆/Li_3-InYb_3-□Se₆. However, no long-range magnetic order is detected in thermomagnetic measurements above 1.8 K due to geometrical frustration. Thus, Li_3-GaYb₃Se₆, Li_3-InYb_3-InSe₆/Li_3-InYb_3-□Se₆, and the LiYbSe₂ previously discovered by our group provide an ideal platform to understand the complex structure-magnetism correlations from 3D to 2D frustrated lattices.