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. Li3-xGaxYb3Se6 and Li3-xInxYb3-yInySe6/Li3-xInxYb3-y□ySe6 crystallize in a trigonal α-NaFeO2 structure-type (space group R3̅m) and can be synthesized using either LiCl or Se flux. In Li3-xGaxYb3Se6, Ga3+ and Li+ are mixed, leaving Yb3+ on the triangular plane. Instead of just Li+ being replaced in Li3-xGaxYb3Se6, In3+ was observed in both the Li+ and Yb3+ layers in Li3-xInxYb3-yInySe6 depending on the reaction conditions. Dominant antiferromagnetic interactions are revealed by magnetic measurements in both Li3-xGaxYb3Se6 and Li3-xInxYb3-yInySe6/Li3-xInxYb3-y□ySe6. However, no long-range magnetic order is detected in thermomagnetic measurements above 1.8 K due to geometrical frustration. Thus, Li3-xGaxYb3Se6, Li3-xInxYb3-yInySe6/Li3-xInxYb3-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.

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