Abstract
► Single phase nanocrystalline Al3+ ions doped Mg–Mn–Ni ferrite have been synthesized by citrate precursor method. ► Particle size decreases as non-magnetic Al content increases. ► The presence of doublets in the Mössbauer spectra can be attributed to superparamagnetic relaxation.
Nanocrystalline Al3+ ions doped Mg0.2Mn0.5Ni0.3AlyFe2−yO4 compositions, where y=0.0, 0.05 and 0.10 have been synthesized by citrate precursor method. Crystal structure and magnetic properties have been investigated at 300K by means of X-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and Mössbauer spectra measurements. XRD study reveals that particle size decreases from 102.25nm to 41.65nm. A decrease in lattice constant and saturation magnetization was attributed to smaller ionic radius of Al3+ ions and weakening of super exchange interaction. Experimental and X-ray density decrease with increasing aluminum concentration. Though Mössbauer spectra of y=0.0 exhibit normal Zeeman split sextets, spectra of samples for y=0.05 and 0.10 are characterized by simultaneous presence of a central paramagnetic doublet. Dependence of Mössbauer parameters such as isomer shift, quadrupole splitting, linewidth and hyperfine magnetic field on Al3+ ions concentration have been discussed. Initial permeability ‘μi’, saturation magnetization (4πMS), retentivity (MR), Bohr magneton number (nBN), magneto crystalline anisotropy constant (K1) and magnetic loss decreases while coercivity (HC) increases with increasing substitution of Al3+ ions. Magnetic loss has very low value in the range of 10−3 which is two orders of magnitude less than samples prepared by conventional method.