Hyperfine Structure ofFe57in Paramagnetic and Antiferromagnetic FeF2from the Mössbauer Effect

Measurements of the gamma-ray resonant absorption in oriented slabs of Fe${\mathrm{F}}_2$ have been used to determine the magnitude and direction of the magnetic field at the iron nucleus in the antiferromagnetic state (3.40×${10}^5$ oe at 0°K) and the quadrupole splitting in the paramagnetic state (31.2 Mc/sec) of this material. The observed electric and magnetic hfs in the antiferromagnetic state is interpretable in terms of an asymmetric electric field gradient tensor with its major axis perpendicular to the $c$ axis, an asymmetry parameter of 0.33, and a quadrupole splitting of 30.3 Mc/sec at 45°K.