Magnetic properties of Zn2+ substituted ultrafine Co-ferrite grown by a sol-gel method

Abstract

Ultrafine Co1−xZnxFe2O4 (0⩽x⩽1.0) particles are fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with x-ray diffraction, vibrating samples magnetometer and Mössbauer spectroscopy. The lattice parameter (a0) increases linearly with increasing Zn concentration (x) and follows Vegard’s law approximately. Co0.9Zn0.1Fe2O4 powders that were annealed at and above 673 K have only a single phase spinel structure and behave ferrimagnetically. Powders annealed at 523 K and 573 K have a typical spinel structure and are simultaneously paramagnetic and ferrimagnetic in nature. The magnetic behavior of Co0.9Zn0.1Fe2O4 powders annealed at and above 573 K shows that an increase of the annealing temperature yields a decrease of the coercivity and an increase of the saturation magnetization. The maximum coercivity and the saturation magnetization of Co0.9Zn0.1Fe2O4 ferrite powders are 1328 Oe and 81.1 emu/g, respectively. Mössbauer spectra of Co–Zn ferrite have been taken at various temperatures from 20 to 800 K. The isomer shifts indicate that the iron ions were ferric at the tetrahedral [A] and the octahedral [B]. The Néel temperature of Co0.9Zn0.1Fe2O4 was determined to be TN=790 K and It is found that Debye temperature for the A and B sites of the sample annealed at 1123 K is found to be ΘA=756±5 K and ΘB=199±5 K, respectively. The Néel temperature dramatically decreased with increasing x from about TN=870 K for x=0.0 to TN=35 K for x=1.0.

Magnetic and Mössbauer Spectroscopy Studies of Zinc-Substituted Cobalt Ferrites Prepared by the Sol-Gel Method

“…When x = 0.7, the Mössbauer spectrum of the sample consisted only of a central doublet, and it exhibited superparamagnetic character. The central doublet can be due to the nonmagnetic nearest neighbors of Fe 3+ ions, as the Fe 3+ ions of magnetic isolation do not take part in long-range magnetic ordering [22,23,24]. …”

“…The Zn 2+ of the 3d 10 electron configuration has a zero angular momentum (l = 0), and it does not contribute to magneto-crystalline anisotropy. From our earlier research [32], the average particle size of CoFe 2 O 4 ( x = 0) is between 85.3 and 102.4 nm, and with increasing Zn content the particle size increases [23,33,34]. The sample’s magneto-crystalline anisotropy decreases with increasing Zn 2+ ions substituted for Co 2+ ions, with subsequent decreases in the coercivity [35,36].…”

Synthesis and magnetic properties of LiFe5O8 powders by a sol–gel process

“…The analysis of the spectra provides very important information about their chemical, structural and magnetic properties from hyperfine interactions, isomer shifts, and quadrupole splitting. It was assumed that all lines had Lorentzian shapes and that the ratio of the areas for each six-line patterns was 3:2:1:1:2:3 [11].…”

Nano-crystalline copper ferrites from secondary iron oxide (mill scale)

“…Various dry methods such as grinding, mechanical alloying and thermal plasma laser pyrolysis have been reported [7,8]. On the other hand, different wet chemical methods such as co-precipitation [2,[9][10][11], hydro-solvothermal synthesis [12][13][14], microemulsion [15,16] and sol-gel techniques [17][18][19] have been used in such preparation. However, the ceramic technique, which involves high-temperature solid-state reactions between the constituent oxides, carbonates or oxalate, was regarded as the most common and easier as well as mass production technique in ferrites synthesis.…”