Nano-magnetic ferrites with composition Mg1−xZnxFe2O4 (x = 0.3, 0.4, 0.5, 0.6, and 0.7) have been prepared by coprecipitation method. X-ray diffraction (XRD) studies showed that the lattice parameter was found to increase from 8.402 to 8.424 Å with Zn2+ ion content from 0.3 to 0.7. Fourier transform infrared (FTIR) spectra revealed two prominent peaks corresponding to tetrahedral and octahedral at around 560 and 430 cm−1 respectively that confirmed the spinel phase of the samples. Transmission electron microscopy (TEM) images showed that the particle size was noted to increase from 18 to 24 nm with an increase in Zn content from x = 0.3 to 0.7. The magnetic properties were studied by vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) which ascertained the superparamagnetic behavior of the samples and contribution of superexchange interactions. The maximum magnetization was found to vary from 23.80 to 32.78 emu/g that increased till x = 0.5 and decreased thereafter. Further, X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical composition and substantiate their oxidation states.
In this paper, effect of Gd 3+ was investigated on structural, magnetic, and dielectric properties of Mn 0.5 Zn 0.5 Gd x Fe 2-x O 4 (x = 0, 0.025, 0.050, 0.075, and 0.1) nanoparticles prepared by facile coprecipitation method. X-ray diffraction (XRD) studies confirmed the single cubic spinel phase for all the samples and showed that lattice parameter (a exp) was found to increase from 8.414 to 8.446 Å with the substitution of Gd 3+ ions due to their larger ionic radii than the replaced Fe 3+ ions. Shape and size of developed nanoparticles were studied using transmission electron microscopy (TEM) and found that particle size decreased from 31.06 to 21.12 nm for x = 0-0.1. Magnetic properties showed that maximum magnetization decreased from 39.21 to 23.59 emu/g, and Curie temperature decreased from 192 to 176 ℃ with increase in x from 0 to 0.1 due to weakening of superexchange interaction. Dielectric parameters like dielectric constant ( and ), dielectric loss (tanδ), AC conductivity (σ ac), and impedance (Z and Z ) as a function of frequency and composition were analyzed and discussed. It was found that , , σ ac , and tanδ values decreased with Gd substitution, which has been explained based on Maxwell-Wagner theory and hopping mechanism of electrons between Fe 3+ and Fe 2+ ions at octahedral sites. Nyquist plots for all the developed compositions showed single semi-circular arc which indicate the dominant effect of grain boundaries.
This paper reports the synthesis of Fe 3 O 4 ferrite nanoparticles and ferrofluid via a coprecipitation method. Structural studies were investigated using X-ray diffraction technique that confirmed the formation of single-phase cubic spinel structure. Morphology and particle size were elucidated using high-resolution transmission electron microscopy. Magnetic characteristics were investigated using a vibrating sample magnetometer, and saturation magnetization of nanoparticles was found to be 23.72 emu/gm with negligible coercivity and retentivity showing superparamagnetic behaviour. A functional self-cooling design employing ferrofluid (as a coolant) was demonstrated in which the system uses heat from the heat source and a permanent magnet to maintain the fluid flow that transfers heat to heat sink. The system is self-regulating and requires no power or pump for flowing of the fluid in the loop. The performance of the device on various parameters like volume fraction of nanoparticles, the temperature of heat source and strength of the magnetic field has also been studied. It was found that cooling by ~ 20 °C was achieved when temperature of heat source was maintained at 85 °C. Cooling performance was enhanced by ~ 7% when the concentration of nanoparticles in ferrofluid was increased from 2 to 6% and by ~ 4% upon the application of magnetic field.
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