A Study on the Properties of Substituted Ferrite (Fe-Al-Ga-Si)

Abstract

Abstract The crystal structure and magnetic properties of a new solid solution type ferrite (Fe 2 O 3 ) 5 -(Al 2 3 3.4 -(Ga 2 3 0.6 -SiOwere investigated using X-ray diffraction and Mossbauer spectroscopy. The results of the X-ray diffraction pattern indicated thatthe crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 A) decreasesslightly with the substitution of Ga 2 O 3 even though the ionic radii of the Ga ions are larger than that of the Al ions. The resultscan 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 beexplained using the observed Mossbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupolesplitting. The drastic change in the magnetic structure according to the Ga ion substitution in the (Fe 2 O 3 ) 5 (Al 2 O 3 ) 4-x (Ga 2 O 3 ) x SiOsystem and the low temperature variation have been studied through a Mossbauer spectroscopy. The Mossbauer spectrum atroom temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures fromthe prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears tooriginate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferredorientation of the crystallites. The Mossbauer spectra below room temperature show various complicated patterns, which canbe explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various andmulti critical. Key words nonstoichiometric ferrite, superparamagnetic clusters, Zeeman pattern, Mossbauer spectroscopy, X-ray diffraction.