Magnetic and structural properties of ultrafine Ni–Zn–Cu ferrite grown by a sol–gel method

Abstract

Ultrafine Ni0.65Zn0.35Cu0.2Fe1.8O4 particles were fabricated by a sol–gel method. The magnetic and structural properties of the powders were investigated with x-ray diffraction, vibrating sample magnetometer, and Mössbauer spectroscopy. Ni–Zn–Cu ferrite powders that were fired at and above 823 K have only a single phase spinel structure and behave ferrimagnetically. Powders annealed at 523, 623, and 723 K have a typical spinel structure and are simultaneously paramagnetic and ferrimagnetic in nature. The magnetic behavior of Ni–Zn–Cu ferrite powders fired at and above 623 K showed that an increase of the annealing temperature yielded a decrease of the coercivity and an increase of the saturation magnetization. The maximum coercivity and the saturation magnetization of Ni–Zn–Cu ferrite powders were Hc=96 Oe and Ms=68 emu/g. Mössbauer spectra of powder annealed at 1223 K were taken at various temperatures ranging from 12 to 675 K. As the temperature increased toward TN, a systematic line broadening effect in the Mössbauer spectra was observed and was interpreted as originating from the different temperature dependencies of the magnetic hyperfine fields at various iron sites. The isomer shifts indicated that the iron ions were ferric at the tetrahedral [A] and the octahedral site [B]. The Néel temperature was determined to be TN=675±2 K.

Effect of heat treatment on the magnetic properties of nanocrystalline spinel Li–Ni ferrite prepared by a simple soft chemistry route

“…5. The saturation magnetization gradually increases with annealing temperature, whereas the coercivity increases with annealing temperature then decreases when the annealing temperature is higher than 800 • C, which is agreement with the literature [20,21]. The changes in the magnetic properties of the Li 0.25 Ni 0.5 Fe 2.25 O 4 ferrites can be attributed to the modification of the particle sizes dependent on the annealing temperature [22].…”

Synthesis and characterization of chitosan coating of NiFe2O4 nanoparticles for biomedical applications

“…The domain structure, critical diameter, and anisotropy of crystal can account for such variation of Hc with particle size. Should it be of a single domain, a crystallite will spontaneously break up into several domains so as to decrease the large magnetization energy it would have [19,35]. Figure 7 illustrates that, in comparison with other nanoparticles, NiFe 2 O 4 nanoparticles (calcined for 120 min) are of higher magnetization and greater magnetic heating loss.…”

“…A decrease in particle size results in a decrease in the number of domains. The particles turn into single domain particles of a size under a critical radius (for nickel ferrite, this parameter is about 100 nm) [35].…”

Investigation of structural and magnetic properties of nanocrystalline Ni0.3Zn0.7Fe2O4 prepared by high energy ball milling

“…Nanocrystalline Ni-Zn ferrite has the extensive applications such as recording heads, antenna rods, loading coils, microwave devices, core material for power transformers in electronics and telecommunication applications due to its improved magnetic behavior and high resistivity and low eddy current losses [3,4]. Because of the reduction of crystallite size (or particle size) to a few nanometers, nanocrystalline soft ferrites exhibit high coercivities and low saturation magnetization [5]. In particular, nanosized mixed ferrites containing zinc have attracted considerable attention.…”