Absolute Spin Magnetic Moment ofFeF2from High Energy Photon Diffraction

The magnetic spin structure factor of ${\mathrm{FeF}}_{2}$ has been directly determined from high energy magnetic x-ray diffraction at 115 keV photon energy. A pure spin moment of $\ensuremath{\mu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4.01(5){\ensuremath{\mu}}_{B}$ was observed, which agrees very well with the spin moment of the free ${\mathrm{Fe}}^{2+}$ ion and differs significantly from values of the total magnetic moment obtained by other methods. The magnetic phase transition of ${\mathrm{FeF}}_{2}$ has been carefully investigated and values for the critical exponent of the order parameter obtained by other techniques have been confirmed.