Neutron Diffraction Investigation of Magnetic Ordering in the Trifluorides of4d-Transition Elements

Mo${\mathrm{F}}_3$ becomes antiferromagnetic below 185°K with a spin-only magnetic moment corresponding to $S=\frac{3}{2}$ and a magnetic structure which can be correlated with coupling rules applicable to the iron-group trifluorides. These results, together with the absence of observable magnetic neutron scattering from Pd${\mathrm{F}}_3$ and Ru${\mathrm{F}}_3$, suggest that Hund's rule does not apply to ions in the $4d$-transition series.