Figure 1: Magnetic properties and anisotropy.

(a) Temperature dependence of the product of the magnetic susceptibility χ times the temperature T for pure (open symbols) and magnetically diluted (solid symbols) samples of (1). Magenta stars are data from ref. 14. The solid line is a theoretical prediction that follows from equation (1). The χT drop observed below 5 K for the pure sample is associated with intermolecular magnetic interactions, which are suppressed upon diluting Co^II with diamagnetic Zn^II. The inset shows the molecular structure of (1). (b) Magnetization hysteresis curves measured at different temperatures on a single crystal of (1) by sweeping the magnetic field along its b crystallographic axis at a rate of 12.6 mT s⁻¹. (c) X-band EPR powder spectrum of the diluted sample, compared with a simulation based on equation (1). (d) Magnetic energy levels of the S=3/2 ground multiplet calculated using the spin Hamiltonian (equation (1)) with a magnetic field applied along the easy axis y (notice the broken energy axis). Below 30 K, the population of the ground electronic doublet exceeds 0.999, thus the system behaves as an effective electronic spin 1/2 system, split by Zeeman and hyperfine interactions. Magenta arrows show EPR transitions between states with the same nuclear spin state (Δm_I=0).