Mössbauer studies and correlation of coercivity with particle morphology in FeSiO2 and FeBN granular solids

Large differences have been observed in the coercivity values of FeSiO2 and FeBN granular films with the coercivities being much lower in the BN matrix. We have used Mossbauer spectroscopy in an attempt to understand the differences in the magnetic hysteresis behavior. The Mossbauer data suggest a core/shell morphology for the FeSiO2 films with an Fe(Fe-Si) core surrounded by an Fe-Si-O shell whose surface consists of Fe2+-Si-O grains. In FeBN the data indicate the presence of amorphous Fe-B particles in a BN matrix. This hypothesized particle morphology can explain the high coercivity values in SiO2 films and the low Hc in BN because of the low anisotropy of the amorphous phase.