Spin-wave stiffness parameter in ferrimagnetic systems: Nanoparticulate powders of (Mg,Zn)Fe2O4 mixed ferrites

Abstract

We have evaluated the spin-wave stiffness parameter in nanoparticulate powders of Mg1−xZnxFe2O4 (0.0≤x≤0.6) mixed ferrites from magnetization data obtained at two different ranges of temperature: 5−300 K and 300−750 K. At the lower temperature range the T-dependence of the saturation magnetization, Ms, data could be fitted to the Bloch's law with T3/2. The spin-wave stiffness parameters D were determined from the coefficient of T3/2; being ∼132 and ∼86 meVÅ for x = 0.0 and 0.6, respectively, with the corresponding exchange constant JAB of ∼1.10 and ∼0.72 meV, respectively. The values of D determined from the experimental Curie temperature Tc were ∼212 and ∼163 meVÅ2 for x = 0.0 and 0.6, respectively, with the corresponding exchange constant JAB of ∼1.77 and ∼1.30 meV. The difference in both JAB and D values obtained from the coefficient of T3/2 and from Tc may be attributed to the fact that the magnetic measurements were performed at a different range of temperatures. The results are discussed in terms of the cation distribution among A- and B-sites of occupation on these spinel ferrites.