Elastic behaviour of mixed manganese-magnesium ferrites

Abstract

of the interatomic and interionic forces in them. Further, a detailed investigation of the dependence of elastic moduli on magnetic field or AE effect is interesting from the stand point of explaining the domain process occurring in the ferrite material. Thus, a study of the dependence of the elastic behaviour of Mn-Mg ferrites on composition and magnetic field at room temperature has been undertaken. The results are presented in this paper. Young's modulus (E) and the rigidity modulus (g) of polycrystalline Mn-Mg ferrites were measured by using the composite oscillator [3]. Mixed Mn-Mg ferrites having the chemical formula Mnl_xMgxFe20 4 (x = 0 to 1) are prepared by the double sintering method. X-ray diffraction patterns for these mixed ferrites have been obtained using CuKa radiation. The lattice constants for ferrites were calculated and it is observed that the variation of lattice constants with composition is linear (Table I). Bulk densities of samples are determined from volume and weight measurements in air at room temperature (30 ° C) are found to be 95% of the corresponding X-ray densities in all the cases. The experimental values of the elastic moduli obtained on porous specimens at room temperature are corrected to theoretical density using the method of Mackenzie [4]. The corrected values of Young's modulus (E) and rigidity modulus (/.t), together with calculated values of the bulk modulus (k), compressibility (fl) and Poisson's ratio (o) are presented in Table I. Following Wooster's work [5] the experimental data are interpreted in terms of the binding forces between the atoms. It can be observed from Table I that an addition of 0.25 tool magnesium ferrite to manganese ferrite has increased the value of the E by about 15%. Similarly an addition of 0.1 mol manganese ferrite to magnesium ferrite has resulted in an increase in E of about 5%. The value of the rigidity modulus is increased by about 15% and 9%, respectively, Further addition of magnesium ferrite to manganese ferrite has also resulted in an increase of the values of E and g. This shows that an addition of a small quantity of magnesium ferrite to manganese ferrite or manganese ferrite to magnesium ferrite has resulted in an increase in the binding forces between the atoms. It can also be observed from the table that the values of k and tr are smaller for mixed magnesium-manganese ferrites of various compositions than for magnesium ferrite.