= Co, Ni.*

Low-dimensional magnetic materials have garnered much attention from theorists and experimentalists alike for many years. Chains of low-spin, ferromagnetically (FM) or antiferromagnetically (AFM) coupled magnetic-ions can both harbour exotic magnetic ground-states: such as the gapped Haldane ground state in Heisenberg AFM chains, or the field-induced quantum paramagnetic state in Ising-like FM chains. In terms of physically realizing such systems, co-ordination chemistry has had great success in promoting crystal architectures that can lead to quasi-1D behaviours. Altering the bridging or non-bridging ligand species can modify both the Heisenberg exchange (J) and single-ion anisotropy (D). It is the interplay of these two parameters that ultimately determines the magnetic ground-state.
To this end, we have recently synthesised two new, highly one-dimensional and isostructural molecule-based magnets; M(NCS)₂(thiourea)₂ [thiourea = CH₄N₂S, M is Co (S = 3/2) or Ni (S=1)]. We employ a combination of magnetometry, heat capacity and muon spin-rotation in addition to theoretical charge density analysis, in an attempt to resolve the magnetic ground-state of both materials.