Generalized Heisenberg-Type Magnetic Phenomena in Coordination Polymers with Nickel–Lanthanide Dinuclear Units

A new family of 3d–4f coordination polymers with the molecular formula [NiIILnIII(L)(dca)2(NO3)]n [Ln = Eu (1), Gd (2), Tb (3), Dy (4), and Ho (5); H2L N,N?-bis(2-hydroxy-3-methoxy-5-methylbenzyl)homopiperazine; dca dicyanamide] has been synthesized in search for single-molecule magnet (SMM) materials containing highly anisotropic lanthanides. The magnetic properties these have established by DC AC magnetometry explained quantitatively comprehensive phenomenological modeling based on a generalized Heisenberg-type model, hypothesized previously first-principles calculations. Single-crystal X-ray diffraction shown that compounds are isostructural, lanthanide atoms occupying nine-coordination site muffin-like geometry individual NiII–LnIII units linked anions. Other than paramagnetic compound 1, 2–5 exhibit intra-unit ferromagnetic interactions, favorable large spin ground state. slow field-induced relaxation magnetization observed 4 (only), displaying substantial energy barrier Ueff/kB 26.2(5) K, below 6 K. This is attributed to an easy-plane anisotropy consistent systems Kramers state doublet hyperfine interactions.