The magnetic susceptibility χ (=M/H) (FC and ZFC) as a function of temperature measured at a low applied field (H=50 Oe) is presented in Fig.5. The molar susceptibility shows a monotonic increase after cooling up to ~22 K, where a steeper increase is observed. Below this temperature a bifurcation between the ZFC and FC curves is evident (see inset of Fig.5). On the other hand and above 22 K the mutual magnetic susceptibility (1/χ) as a function of temperature shows a linear trend (Fig. 5 right scale). In detail, above about 30 K, in the paramagnetic region, the Curie-Weiss law is rigorously followed by fitting the linear part of the 1/χ curve with 1/χ = (T-p) /C, in the interval of temperatures 30-310 K, a Curie-Weiss temperature, p = -2.3 K, and the Curie constant, C = 1.30 cm3.K.mol-1, (μeff = 3, 2 µB). The small negative Curie-Weiss temperature indicates the presence of weak antiferromagnetic exchange interactions between the magnetic centers of Ni. In fact, the χT curve (Fig. 6 left scale) shows a downward curvature, typical of systems with non-negligible antiferromagnetic and/or spin-correlations. orbital coupling The χT=1.31 cm3.K.mol-1 at 310 K undergoes a small and gradual decrease to 1.19 emu.K.mol-1 at 24.5 K. The value of the Curie, obtained by 1/χ linear fit or by linear fit. The product χT for T>>p is in reasonable agreement with the theoretical spin-only value expected for NiII in an octahedral environment with spin state S=1 (C = 1 cm3.K.mol-1e µeff = 2.83 µB considering g = 2 ) for unquenched orbital momentum C = 3.91 cm3.K.mol-1e µeff = 5.59 µB).Fig. 5Fig. 6With further cooling, the χT curve shows a sudden increase to 1.23 cm3.K.mol-1 at T=21 K followed by a sharp decrease to 0.71 cm3.K.mol-1 at 5 K. The maximum χT of... ... middle of paper ...... magnetic orbitals on the metal and valence orbitals of the ligands. In the present case, where the nickel centers are bridged by long NCN hmt and NCNCN dca ligands, it is reasonable to assume that only minor exchange interactions can be mediated by these bridges and, as observed here, these types of magnetic pathways generally promotes antiferromagnetic interactions. 38,45-48]. However, spin tilting is often observed and usually associated with single ion magnetic anisotropy or antisymmetric exchange interaction. From structural considerations, the existence of two crystallographically independent Ni(II) ions with non-collinear axes of anisotropy could be at the origin of the suspected canting phenomena. To clearly ascertain the existence of a swinging spin magnetic order, as the data suggest, neutron diffraction measurements are planned.4. Conclusion