Structural Complexity and Magnetic Orderings in a Large Family of 3d–4f Heterobimetallic Sulfates

The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among Ln2O3, CuO, and H2SO4, giving rise to four distinct phases, namely Ln2Cu(SO4)2(OH)4 (Ln = Sm-Ho) (LnCuSO4-1), Ln4Cu(SO4)2(OH)10 (Ln = Tm-Lu) (LnCuSO4-2), LnCu(SO4)(OH)3 (Ln = Nd-Gd, except Pm) (LnCuSO4-3), and LnCu(SO4)(OH)3 (Ln = Dy-Lu) (LnCuSO4-4), with completely different topologies. The passage from LnCuSO4-1 and LnCuSO4-3 to LnCuSO4-2 and LnCuSO4-4 across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln3+ cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in GdCuSO4-3 and HoCuSO4-4 to antiferromagnetic ordering in YbCuSO4-4, and to paramagnetic correlations found in GdCuSO4-1 and YbCuSO4-2.