Magnetically induced electric field gradients

Several investigations of the Mössbauer spectrum of Fe₂As have yielded results which do not agree with those obtained by neutron diffraction studies. We report here a new investigation, and we show that the earlier disagreement is caused by a lack of appreciation of several factors. These include fluctuating hyperfine magnetic fields (relaxation) and an asymmetry of the electric field gradient produced by the spontaneous magnetization.On leave of absence at Laboratoire de Spectroscopie Hertzienne de l'Ecole Normale Superieure, 24 Rue Lhomond, 75005 Paris, France