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 LiYbSe₂into a triangular lattice by doping Ga or In. Li_3-xGa_xYb₃Se₆and Li_3-xIn_xYb_3-yIn_ySe₆/Li_3-xIn_xYb_3-y□_ySe₆crystallize in a trigonal α-NaFeO₂structure-type (space group R3¯ m) and can be synthesized using either LiCl or Se flux. In Li_3-xGa_xYb₃Se₆, Ga³⁺and Li⁺are mixed, leaving Yb³⁺on the triangular plane. Instead of just Li⁺being replaced in Li_3-xGa_xYb₃Se₆, In³⁺was observed in both the Li⁺and Yb³⁺layers in Li_3-xIn_xYb_3-yIn_ySe₆depending on the reaction conditions. Dominant antiferromagnetic interactions are revealed by magnetic measurements in both Li_3-xGa_xYb₃Se₆and Li_3-xIn_xYb_3-yIn_ySe₆/Li_3-xIn_xYb_3-y□_ySe₆. However, no long-range magnetic order is detected in thermomagnetic measurements above 1.8 K due to geometrical frustration. Thus, Li_3-xGa_xYb₃Se₆, Li_3-xIn_xYb_3-yIn_ySe₆/Li_3-xIn_xYb_3-y□_ySe₆, and the LiYbSe₂previously discovered by our group provide an ideal platform to understand the complex structure-magnetism correlations from 3D to 2D frustrated lattices.