Investigation of structural and magnetic properties of co-precipitated Mn–Ni ferrite nanoparticles in the presence of α-Fe₂O₃ phase

A systematic study on structural and magnetic properties of co-precipitated MnxNi1-xFe2O4 (x=0.5, 0.6, 0.7) ferrite nanoparticles annealed at 800 °C was carried out using XRD, FE-SEM, VSM and MöSSBAUER techniques. Anti-ferromagnetic α-Fe2O3 phase was observed along with the magnetic spinel phase in the XRD patterns. It is observed that both lattice parameter and crystallite size of spinel phase increase with increase in concentration of Mn2+ along with the amount of α-Fe2O3 phase. The saturation magnetization (Ms) decreases while coercivity (Hc) increases with increase of Mn2+ ion concentration. Mössbauer spectra indicate that iron ions present in A and B sites are in the Fe3+ state and Fe2+ is absent. The results are interpreted in terms of observed anti-ferromagnetic α-Fe2O3 phase, core–shell interactions and cation redistribution

Structural, thermal and magnetic studies of Mg<SUB>x</SUB>Zn<SUB>1-x</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> nanoferrites: study of exchange interactions on magnetic anisotropy

Polycrystalline nanoferrites with chemical formula MgxZn1-xFe2O4 (x=0.5, 0.6, 0.7) have been synthesized by co-precipitation technique and then subsequently heated to 800&#176;C in order to investigate structural, thermal and magnetic properties. The samples are characterized by using XRD, FTIR, TGA-DSC, SQUID and Mossbauer spectroscopy techniques. The synergic effect of heat treatment with substitution of Mg2+, results in random variation of lattice parameter (a) and crystallite size (D). FTIR studies revealed the formation of cubic spinel structure. The broadening at octahedral bands for compositions x=0.6 and 0.7 attributes to distribution of ferrite particles of different sizes in these samples. The characteristic feature of hysteresis loops reflects the nature of ferrite particles in the state of superparamagnetism. The saturation magnetization at room temperature has been reported for composition x=0.7 is 44.03 emu/g. The variation of coercivity is due to variation in magnetic anisotropy which is predominately affected by the exchange interactions arising from the nature of nanoparticles. The blocking temperatures are in the range of 10–30 K and their variation is in the line of change in magnetocrystalline anisotropy but not due to variation in crystallite sizes. The Zeeman splitting at tetrahedral (A) and octahedral (B) sites for composition x=0.6 is expected due to increase in size of core of the nanoparticles/or increasing of magnetocrystalline anisotropy. The range of isomer shift values and quadruple splitting values are evident for the presence of Fe3+ ions and the absence of Fe2+ ions in the present systems. The present ferrite nanoparticles in the superparamagnetic state are the potential candidates for biomedical applications like cancer treatment through hyperthermia. The results are interpreted in terms of cation redistribution presuming exchange coupling energy variation on magnetocrystalline anisotropy

Structural and magnetic characterization of co-precipitated Ni_XZn_1-XFe₂O₄ ferrite nanoparticles

A series of Ni_XZn_1-XFe₂O₄ (x=0.5, 0.6 and 0.7) ferrite nanoparticles have been synthesized using a co-precipitation technique, in order to understand the doping effect of nickel on their structural and magnetic properties. XRD and FTIR studies reveal the formation of spinel phase of ferrite samples. Substitution of nickel has promoted the growth of crystallite size (D), resulting the decrease of lattice strain (&#951;). It was also observed that the lattice parameter (a) increases with the increase of Ni²⁺ ion concentration. All particles exhibit superparamagnetism at room temperature. The hyperfine interaction increases with the increase of nickel substitution, which can be assumed to the decrease of core–shell interactions present in the nanoparticles. The M&#246;ssbauer studies witness the existence of Fe³⁺ ions and absence of Fe²⁺ ions in the present systems. These superparamagnetic nanoparticles are supposed to be potential candidates for biomedical applications. The results are interpreted in terms of microstructure, cation redistribution and possible core–shell interactions