New Nabokoite‐like Phases ACu₇TeO₄(SO₄)₅Cl (A=Na, K, Rb, Cs) with Decorated and Distorted Square Kagome Lattices

Abstract

A new family of compounds ACu7TeO4(SO4)5Cl (A=Na, K, Rb, Cs) isostructural to mineral Nabokoite (K species) was synthesized by solid state and gas transport reactions in sealed ampoules and characterized in measurements of magnetization and specific heat in a wide temperature range. These complex compounds are of the utmost interest as a testing playground to study the properties of quasi‐two‐dimensional magnets with a square kagome lattice geometry. A quantum ground state of such a corner‐sharing network is a spin liquid. Unlike idealized grid analyzed in numerous models, the square kagome lattice in nabokoites is wavy and distorted being composed of versatile triangles. Moreover, it contains “excessive” decorating magnetic ions, which makes magnetism of these objects even more complicated. The interaction of these decorating ions through virtual excitations of the square kagome lattice is accompanied by the formation of a long‐range magnetic order coexisting with the spin liquid.

Exotic magnetization curves in classical square-kagomé spin lattices

“…A similar spin system on a lattice with corner-sharing triangles is the square-kagomé Heisenberg antiferromagnet (SKHAF), that was introduced about 20 years ago [8][9][10][11][12][13][14][15][16][17][18]. Over the past five years, this system has attracted increasing attention in theoretical [19][20][21][22][23][24][25][26][27][28] as well as experimental [29][30][31][32][33] investigations. The discovery of a liquid spin phase in the square kagomé magnet Na 6 Cu 7 Bi O 4 (PO 4 ) 4 Cl 3 [28,30] and in the nabokoite family compounds K Cu 6 Al Bi O 4 (SO 4 ) 5 Cl [29,[32][33][34] provides a particular motivation to investigate this model.…”