Chemical Pressure Tuning Magnetism from Pyrochlore to Triangular Lattices

Abstract

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-xGa_xYb₃Se₆ and Li_3-xIn_xYb_3-yIn_ySe₆/Li_3-xIn_xYb_3-y□_ySe₆ crystallize in a trigonal α-NaFeO₂ structure-type (space group R3̅m) 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_ySe₆ depending on the reaction conditions. Dominant antiferromagnetic interactions are revealed by magnetic measurements in both Li_3-xGa_xYb₃Se₆ and 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 LiYbSe₂ previously discovered by our group provide an ideal platform to understand the complex structure-magnetism correlations from 3D to 2D frustrated lattices.