Mixed Kagomé and Triangular Lattices in Transition Metal Sulfate Compounds M7(SO4)3(OH)8 (M = Co, Ni, Cu)

A series of transition metal sulfate compounds, M7(SO4)3(OH)8 (M = Co, Ni, Cu), have been hydrothermally synthesized and exhibit unique topological spin lattices composed of mixed kagomé and triangular motifs. Co7(SO4)3(OH)8 and Ni7(SO4)3(OH)8 feature alternating kagomé and triangular layers along the c-axis, while Cu7(SO4)3(OH)8 shows merged kagomé and triangular motifs extending along the a-axis due to greater octahedral distortion. Magnetic measurements reveal that Co7(SO4)3(OH)8 exhibits a ferrimagnetic transition at ∼6.5 K with strong frustration, while Ni7(SO4)3(OH)8 undergoes long-range magnetic order at ∼24 K and exhibits spin-glass behavior at ∼2.5 K.