UnconventionalS=2alternating chain realized by a metal-radical hybrid-spin approach

We demonstrate an advanced spin-system design using a hybrid spin consisting of a strongly coupled metal ion and verdazyl radical. Ab initio calculation, magnetization, and ESR measurements evidenced the first realization of an $S=2$ ferromagnetic-antiferromagnetic alternating chain with Ising anisotropy in a Mn-verdazyl complex $\left[{\mathrm{Mn}\left(\mathrm{hfac}\right)}_2\right]·(o-\mathrm{Py}-\mathrm{V})$ [hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate; o-Py-V = 3-(2-pyridyl)-1,5-diphenylverdazyl]. Furthermore, we find an anomalous change in magnetization at 1/4 of the saturation value, which is probably a manifestation of the quantum nature of the system.