Magnetic and hyperfine properties of nanocrystalline Ni_0.2Zn_0.6Cu_0.2Fe₂O₄prepared by a chemical route

Abstract

Nanoparticles of Ni0.2Zn0.6Cu0.2Fe2O4 were prepared by the standard co-precipitation method. The formation of nanocrystalline mixed spinel phase has been confirmed by x-ray diffractograms. The sizes of the nanoparticles were estimated in the range 7–30 nm, which was confirmed by transmission electron microscopy. Thermal variations of the real part of AC magnetic susceptibilities measured from 450 K down to 80 K and Mössbauer effect measurements at room temperature and down to 20 K clearly indicate the presence of superparamagnetic particles in all the samples. Specific saturation magnetizations measured by VSM are found to increase steadily with the increase of average particle size. The coercive field obtained from low frequency measurements shows that in all the samples a small fraction of particles is not relaxed within the measuring time. For samples showing a less dominating superparamagnetic behaviour, AC magnetic susceptibility data showed the expected increase of blocking temperature with increase in particle size. Magnetic anisotropy energy constants of the nanoparticles were estimated from the blocking temperature and the values cannot be directly correlated with their particle sizes.

XRD, HRTEM and magnetic properties of mixed spinel nanocrystalline Ni–Zn–Cu-ferrite

“…Thus with the rise of annealing temperature redistribution of zinc cation between tetrahedral and octahedral site induces a change in the variation of lattice parameters (Table 1). Although this sort of behaviour has also been observed in our pre- vious study where cationic inversion is observed at about 700 • C [14].…”

“…where the symbols have their usual meanings [14].ˇ1 /2 = (ˇ1 /2 ) 2 0 − b 2 0 , where (ˇ1 /2 ) 0 is the full width at half maximum (FWHM) of the (3 1 1) peak and b 0 is the same for large crystallites. Value of (ˇ1 /2 ) 0 is obtained from the fitting of the (3 1 1) peak to Lorentzian function and the uncertainties in the particle sizes are estimated from the errors in the Lorentzian fitting procedures, which lie in the range ±1 nm.…”

“…The stoichiometric ratio of Fe:Ni:Zn:Cu are taken as 2:0.4:0.4:0.2. The details of the preparation are discussed in our earlier paper [14]. The as prepared samples are dried at 100 • C for 24 h. The dried samples are annealed in air at various temperatures to obtain the desired mixed spinel ferrite of different particle sizes.…”

“…The addition of CuO not only influences the magnetic properties but also influences the sintering temperature, ferrite density, etc. In our previous report [14] we have investigated the magnetic and hyperfine properties of the nanocrystalline Ni 0.2 Zn 0.6 Cu 0.2 Fe 2 O 4 , where the soft magnetic properties are enhanced compared to Caizer and Stefanescu [10]. In the previous report on the nanocrystalline Ni 0.2 Zn 0.…”

“…Although the common criteria for every application are the lowest magnetic loss due to which high resistivity is needed for these materials. In this regard Ni-Zn-ferrite/Ni-Zn-Cu-ferrite is highly suited for their applications as soft magnetic materials because of low coercive field, high-resistivity and low-production cost [10][11][12][13][14].…”