Synthesis of a d¹-titanium fluoride kagome lattice antiferromagnet

The kagome lattice, composed of a planar array of corner-sharing triangles, is one of the most geometrically frustrated lattices. The realization of a spin S = 1/2 kagome lattice antiferromagnet is of particular interest because it may host an exotic form of matter, a quantum spin liquid state, which shows long-range entanglement and no magnetic ordering down to 0 K. A few S = 1/2 kagome lattice antiferromagnets exist, typically based on Cu²⁺, d⁹ compounds, though they feature structural imperfections. Herein, we present the synthesis of (CH₃NH₃)₂NaTi₃F₁₂, which comprises an S = 1/2 kagome layer that exhibits only one crystallographically distinct Ti³⁺, d¹ site, and one type of bridging fluoride. A static positional disorder is proposed for the interlayer CH₃NH₃⁺. No structural phase transitions were observed from 1.8 K to 523 K. Despite its spin-freezing behaviour, other features-including its negative Curie-Weiss temperature and a lack of long-range ordering-imply that this compound is a highly frustrated magnet with unusual magnetic phase behaviours.