where M s is saturation magnetisation and taking into account the fact the measured remnant magnetisation is a powder-average (Fig. ). The saturation magnetisation was determined using the g-factor from Curie-Weiss analysis M s = gSµ B (Tab. 1). This gives γ = 9.1(4) • for NiCl 2 (pym) and 6.4(3) • nd NiCl 2 (btd). For FeCl 2 (pym) the small coercive field means we use an effective remnant magnetisation defined by the extrapolation of the hysteresis loop from M (µ 0 H = 0.1) to zero field M ′ r = 0.44(1)µ B , giving γ = 16.0(6) • . As there is no stable state for FeCl 2 (btd) with a net moment, we are unable to carry out equivalent analysis.