SPIN REORIENTATION IN SUBSTITUTED IRON GARNETS INVESTIGATED BY MOSSBAUER SPECTROMETRY

Substituted iron garnets exhibiting very high magnetic permeability pr operties were investigated by Fe-57 Mossbauer spectrometry. The temper ature dependences of the hyperfine field and the quadrupole shift at t he different iron sites suggest the existence of a distribution of spi n reorientation transitions, distribution attributed to the cationic s ubstitution. This phenomenon which is in qualitative agreement with pe rmeability measurements, is attributed to the introduction of scandium and terbium cations in the iron and yttrium sublattices, respectively . The hyperfine data are consistent with a gradual change of the easy magnetization axis from the [100] to [111] directions with increasing temperatures. The cationic distribution resulting from the octahedral and tetrahedral iron site occupancies differs from that encountered in pure iron garnets.