Magnetism of coupled spin tetrahedra in ilinskite-type KCu${}_5$O${}_2$(SeO${}_3$)${}_2$Cl${}_3$

Synthesis, thermodynamic properties, and microscopic magnetic model of ilinskite-type KCu${}_5$O${}_2$(SeO${}_3$)${}_2$Cl${}_3$ built by corner-sharing Cu${}_4$ tetrahedra are reported, and relevant magnetostructural correlations are discussed. Quasi-one-dimensional magnetic behavior with the short-range order around 50,K and the absence of long-range order down to at least 2,K is observed experimentally and explained in terms of weakly coupled spin ladders (tubes) with a complex topology formed upon fragmentation of the tetrahedral network. This fragmentation is rooted in the non-trivial effect of the SeO${}_3$ groups that render the Cu–O–Cu superexchange strongly ferromagnetic.