Spin-wave fluctuations in ferrimagnetic MgxFe3−xO4 nanoparticles

We have performed a systematic study of the magnetic properties of a series of ferrimagnetic nanoparticles of MgxFe3−xO4 (0.8≤x≤1.5) prepared by the combustion reaction method. The magnetization data can be well fitted by Bloch’s law with T3/2. Bloch’s constant B determined from the fitting procedure was found to increase with Mg content x from ∼3.09×10−5 K−3/2 for x=0.8 to 6.27×10−5 K−3/2 for x=1.5. The exchange integral JAB and the spin-wave stiffness constant D of MgxFe3−xO4 nanoparticles were also determined as ∼0.842 and 0.574 meV and 296 and 202 meV A2 for specimens with x=0.8 and 1.5, respectively. These results are discussed in terms of cation redistribution among A and B sites on these nanostructured spinel ferrites.