FeCl 2 (pym) and NiCl 2 (pym) have the unusual combination of an antiferromagnetic ground state and magnetic hysteresis leading to remnant magnetism and a metastable zero-field ferromagnetic state. The presence of hysteresis is well known around the metamagnetic transition, including even in canonical metamagnet FeCl 2 and in the related collinear NiCl 2 L, 25 however the presence of metamagnetic hysteresis significant enough that the ferromagnetic state is stable without field is very rare, having been previously reported for two layered brucite cobalt hydroxides, Co 2 (OH) The coercive fields of NiCl 2 (pym) (in its ferromagnetic phase) and NiCl 2 (btd) are very large, both compared to other compounds and FeCl 2 (pym). Indeed, H C = 1.8 T at 2 K for NiCl 2 (pym) is much larger than other vdW ferromagnets, even hard ferromagnets such as VI 3 (H C = 0.9 T). The origin of this lies both with single-ion anisotropy and the magnetocrystalline anisotropy (MCA). As discussed below, Ni(II) is likely to have easyaxis, and Fe(II) easy-plane anisotropy, which suggests that the single-ion anisotropy contribution to coercivity will be larger for Ni(II).