Mossbauer study of nanostructured iron fluoride powders

Nanostructured iron fluoride powders were prepared using the grinding route for different times and different intensities. Their structural, microstru ctural and magnetic properties are investigated by means of both transmissi on Mossbauer spectrometry as a function of temperature and in-held Fe-57 Mo ssbauer spectrometry. We report a fitting procedure which successfully desc ribes the zero-field Mossbauer spectra recorded at different temperatures. It allows us to describe the powders as crystalline grains and grain bounda ries which behave as antiferromagnets and speromagnets, respectively. Such arrangements are confirmed by in-field Mossbauer spectrometry. According to x-ray diffraction data, the size of grains and the thickness of grain boun daries are found to be strongly dependent on the grinding conditions. The o ccurrence of superparamagnetic effects at high temperature gives clear evid ence for the role of grain boundaries in the magnetic coupling of crystalli ne grains.