Abstract
The magnetic susceptibilities parallel and perpendicular to the chain axis have been measured in the three linear ferromagnets TMNC, TMNB and CsNiF3 between 1.2 and 77K. Strong anisotropy is observed at low temperature. The variation of chi //c with temperature is in good agreement with the predictions of the quantum given by de Neef. This allows a determination of the parameters J and D in these salts: in CsNiF3 J=10+or-0.5K, D=8.5+or-0.5K; in TMNC, J=1.7+or-0.3K, D=3.4+or-0.5K; in TMNB, J=4.8+or-0.2K, D=3.4+or-0.5K. In the 3D long-range ordered state, a study of the variation with temperature of the spontaneous sublattice magnetisation has been performed by NMR; the curves reflect the existence of an anisotropy in the ab plane in TMNC and TMNB, but not in CsNiF3.