Structure and magnetic properties of granular NiZn-ferrite - SiO2

Abstract

Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthesized by sol-gel processing. Samples with ferrite volumetric fraction x ranging from 6% to 78% were prepared, and characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Our results show the formation of pure stoichiometric NiZn-ferrite in the SiO2 matrix for x < 34%. Above these fraction, our samples presented also small amounts of Fe2O3. Mössbauer spectroscopy revealed the superparamagnetic behaviour of the ferrimagnetic NiZn-ferrite nanoparticles. The combination of different ferrite concentration and heat treatments allowed the obtaintion of samples with saturation magnetization between 1.3 and 68 emu/g and coercivity ranging from 0 to 123 Oe, value which is two orders of magnitude higher than the coercivity of bulk NiZn-ferrite

Structure and magnetic properties of NiZn ferrite/SiO2 nanocomposites synthesized by ball milling

“…This last value of H iC is the highest one obtained in this work and is near two orders of magnitude higher than the corresponding value for bulk NiZnferrite [17] and almost three times higher than the coercivity measured for a similar NiZn-ferrite/SiO 2 nanocomposite synthesized by sol-gel processing [25]. This high value of coercivity in sample M260Ar is attributed to an increase of the mean size of the NiZn-ferrite crystallites embedded in the amorphous silica matrix, as compared to samples M80air and M60air.…”

Development of Ni–Zn nanoferrite core material with improved saturation magnetization and DC resistivity

“…The saturation magnetization value in present work has been observed to be higher than any other reported value of same composition or nearby compositions as evident from Table 1. There have been many available reports [21][22][23][24][25][26][27][28][29][30][31] especially on Ni-Zn nanoferrites of composition close to the present composition, indicating less values of saturation magnetization than that observed. The observed higher value of saturation magnetization can be explained on the basis of grain size and the exchange interaction among the adjacent nanograins.…”

Role of Cr3+ ions on the microstructure development, and magnetic phase evolution of Ni0.7Zn0.3Fe2O4 ferrite nanoparticles

“…However, the formula (A 1−i B i )[AiB 2−I ]O 4 represents many possible intermediary distributions that denote considerable cation disorder, indicating that this structure requires special attention in terms of magnetic characterization [10]. The Ni-Zn ferrite is a well-known mixed inverse spinel [11] whose unit cell is represented by the formula (Zn x Fe 1−x )[Ni 1−x Fe 1+x ]O 4 [12,13], whereas the intrinsic magnetization (magnetic moment or total theoretical Bohr magneton of the lattice spinel) results from the inverse and normal phase, i.e., the distribution of cations in the spinel lattice. Based on these facts, the intrinsic magnetization of Ni-Zn ferrite can be calculated with and without the addition of 0.1 mol of chromium ions.…”