The crystal structure and magnetic properties of a new solid solution type ferrite (Fe2O3)5-(Al2O3)3.4-(Ga2O3)0.6-SiO were investigated using X-ray diffraction and Mössbauer spectroscopy. The results of the X-ray diffraction pattern indicated that the crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 Å) decreases slightly with the substitution of Ga2O3 even though the ionic radii of the Ga ions are larger than that of the Al ions. The results can be attributed to a higher degree of covalency in the Ga-O bonds than in the Al-O and Fe-O bonds, which can also be explained using the observed Mössbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupole splitting. The drastic change in the magnetic structure according to the Ga ion substitution in the (Fe2O3)5(Al2O3)4-x(Ga2O3)xSiO system and the low temperature variation have been studied through a Mössbauer spectroscopy. The Mössbauer spectrum at room temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures from the prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears to originate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferred orientation of the crystallites. The Mössbauer spectra below room temperature show various complicated patterns, which can be explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various and multi critical.

• 최승한 | Choi, Seung-Han