Data for Magnetic ground state of the one-dimensional ferromagnetic chain compounds M(NCS)2(thiourea)2 (M=Ni,Co)

The magnetic properties of the two isostructural molecule-based magnets, Ni(NCS)2(thiourea)2,S = 1, [thiourea = SC(NH2)2] and Co(NCS)2(thiourea)2, S = 3/2, are characterised using several techniques in order to rationalise their relationship with structural parameters and ascertain magnetic changes caused by substitution of the spin. Zero-field heat capacity and muon-spin relaxation measurements reveal low-temperature long-range ordering in both compounds, in addition to Ising-like (D < 0) single-ion anisotropy (DCo ∼ -100 K, DNi ∼ -10 K).

Crystal and electronic structure, combined with DC-field magnetometry, affirm highly quasi-one-dimensional behaviour, with ferromagnetic intrachain exchange interactions J Co ≈ + 4 K and J Ni ∼ + 100 K and weak antiferromagnetic interchain exchange, on the order of J 0 ∼ − 0.1 K. Electron charge and spindensity mapping reveals through-space exchange as a mechanism to explain the large discrepancy in J-values despite, from a structural perspective, the highly similar exchange pathways in both materials.