Mn-Zn ferrite nanoparticles have been subject of increasing research due to their desired properties for a wide range of applications. These properties include nanometer particle size control, tunable magnetic properties and low toxicity, providing these ferrites with the necessary requirements for cancer treatment via magnetic hyperthermia. During this master thesis, powders of Mn1-xZnxFe2O4 (x=0; 0.5; 0.8; 1) were synthesized via the sol-gel autocombustion and hydrothermal methods, aiming to optimize their structural and magnetic properties for further application in a ferrofluid. Samples were characterized by XRD, SQUID, SEM, TEM and magnetic induction heating (MIH) techniques. The XRD diffractograms of hydrothermally produced samples present spinel crystal structure with high single-phase percentage (>88%). Rietveld refinement and Williamson-Hall analysis reveal a decrease of lattice constant and crystallite size with increase of Zn/Mn ratio. TEM images reveal narrow particle size distributions and decrease of the mean particle size with increase of Zn/Mn. SQUID results show that the increase of Zn results in a decrease of saturation magnetization and remnant magnetization. More noticeably, the M(T) curves present a shift in the samples magnetic ordering temperature towards lower temperatures with the increase of Zn content, from ~556 to ~284 K. The MIH experiment also unveil a decrease in the heating rate with the increase of Zn. Nanocrystals of Mn-Zn ferrite produced by hydrothermal method present better crystallinity and magnetic properties than the sol-gel auto-combustion samples. The hydrothermally synthesized samples revealed dependence of its structural and magnetic properties with Mn/Zn ratio.The magnetic ordering temperature of these ferrites can be used as a self-controlled mechanism of heating, raising these ferrites to a class of smart materials.
The method of microwave assisted hydrothermal synthesis of bismuth ferrite multiferroic nanoflowers, their mechanism of growth, magnetic as well as dielectric properties are presented. The nanoflowers are composed of numerous petals formed by BiFeO3 (BFO) nanocrystals and some amount of amorphous phase. The growth of the nanoflowers begins from the central part of calyx composed of only few petals towards which subsequent petals are successively attached. The nanoflowers exhibit enhanced magnetization due to size effect and lack of spin compensation in the spin cycloid. The dielectric properti…
In this work, a successful synthesis of magnetic cobalt ferrite (CoFe2O4) nanoparticles is presented. The synthesized CoFe2O4 nanoparticles have a spherical shape and highly monodisperse in the selected solvent. The effect of different reaction conditions such as temperature, reaction time and varying capping agents on the phase and morphology is studied. Scanning transmission electron microscopy showed that the size of these nanoparticles can be controlled by varying reaction conditions. Both X-ray diffraction and energy dispersive X-ray spectroscopy corroborate the formation of CoFe2O4 spine…
Spinel Ferrite-Based Materials for Electrochemical Applications: Synthesis, Applications, and Future Perspectives
Guru Ghasidas Vishwavidyalaya (A Central University)（古鲁·格哈西达斯大学（一所中央大学））；Government Girls Degree College Samadi（萨马迪女子政府学位学院）；Indian Institute of Technology (BHU)（印度理工学院（贝拿勒斯印度教大学））；Indian Institute of Technology Bhilai（印度理工学院比莱分校）
We report the synthesis and characterization of original 'multishell' magnetic nanoparticles made of a soft core (magnetite) covered with two successive shells: a hard one (cobalt ferrite) and then a soft one (manganese ferrite). Our results show that contrary to expectations from simple models in which the coercivity of a bimagnetic core/shell nanoparticle depends simply on the proportion of soft and hard phases within that particle, the addition of a second shell made of a soft ferrite material enhances the coercivity. Taking into account the interactions between the shells themselves and th…
Zn doped Mn ferrites nanoparticles were fabricated by using Co-precipitation. Variation in structure, magnetic and optical properties of MnZn ferrites has been discussed. First of all, samples were synthesized, annealed at different temperatures and then characterized. The as-synthesized and annealed samples were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy Dispersive spectroscopy (EDX), Ultra Violet visible spectrometry (Uv-Vis spectrometry) and Vibrating sample magnetometer (VSM). The average crystallite size of MnZn ferrites nanoparticles determined fr…
We present a simple, scalable synthesis route for producing exchange coupled soft/hard magnetic composite powder that outperforms pure soft and hard phase constituents. Importantly, the composites is iron oxide based (SrFe12O19 and Fe3O4) and contain no rare earth or precious metal. The two step synthesis process consists of first precipitating, an Iron oxide/hydroxide precursor directly on top of SrFe12O19 nano-flakes, ensuring a very fine degree of mixing between the hard and the soft magnetic phases. We then use a second step that serves to reduce the precursor to create the proper soft mag…
This study reports on the synthesis of ball-like bismuth ferrite BiFeO3 nanoflowers by means of microwave assisted hydrothermal process and also on their composition and mechanism of growth. It turns out that the petals of the nanoflowers are composed of the nanocrystals with the size about 35-39 nm whereas their thickness and size depends on the concentration of surfactants. The petals contain BiFeO3 phase and traces of Bi2O3 oxide and metallic Bi and Fe deposited mainly at their surface. Amounts of impurity phases are more pronounced in nanoflowers synthesized during short time, and become a…
Bi3+ Doped Nanocrystalline Ni-Co-Zn Spinel Ferrites: Tuning of Physical, Electrical, Dielectric and Magnetic Properties for Advanced Spintronics Applications
Nanometer copper ferrite, as a kind of nanometer particle with catalytic activity, and its photothermal and magnetothermal effects as ferrite, can be widely used in different fields. It is a general way to obtain the nano effect of the target by controlling the particle size. In this paper, the crystallization process of hydrothermal/solvothermal synthesis was analyzed, and the nucleation model was established to simulate the effects of solvent, reaction temperature and cooling time on the particle size of copper ferrite nanoparticles. Through Monte Carlo method and energy function, the ratio …
Magnetoelectric Coupling in Nickel-Cobalt Ferrite and Lanthanum Ferrite Heterostructure Composites: Experimental Evidence and Simulation-Driven Insights
In-depth investigations of size and occupancies in cobalt ferrite nanoparticles by joint Rietveld refinements of X-ray and neutron powder diffraction data
In this paper, the photocatalytic activity of multiferroics BiFeO3 (BFO) and Bi0.8La0.2FeO3 (BLFO) nanocrystals with two different morphologies which were synthesized by two different sol-gel (SG) and hydrothermal (HT) methods have been studied. All the obtained samples were characterized using X-ray diffractometer, Fourier transform infrared spectroscopy, transmission electron microscopy, UV-vis spectroscopy and vibrating sample magnetometer. Differential thermal analysis (DTA) measurements were probed ferroelectric- paraelectric first-order phase transition (TC) for all samples. Addition of …
Single phase barium titanate-bismuth ferrite ((1-x)BaTi$_3$-(x)BiFe$_3$, BTO-BFO) solid solutions were prepared using citric acid and ethylene glycol assisted sol-gel synthesis method. Depending on the dopant content the samples are characterized by tetragonal, tetragonal-pseudocubic, pseudocubic and rhombohedral structure as confirmed by Raman spectroscopy and XRD measurements. An increase of the BFO content leads to a reduction in the cell parameters accompanied by a decrease in polar distortion of the unit cell wherein an average particle size increases from 60 up to 350 nm. Non zero piezor…
Super-paramagnetic nanoparticles (NPs) have been widely explored as magnetic resonance imaging (MRI) contrast agents because of a combination of favorable magnetic properties, biocompability and ease of fabrication. MRI using traditional T1- or T2-weighted single mode contrast-enhanced techniques may yield inaccurate imaging results. In the present work, a T1/T2 dual mode contrast agent based on the super-paramagnetic zinc-manganese ferrite (Zn$_{0.3}$Mn$_x$Fe$_{2.7-x}$O$_4$, x= 0, 0.25, 0.75 and 1) NPs with small core size and a hydrophilic PEG surface coating is reported. The TEM, TGA and FT…
We report the synthesis of Y-substituted Mg-Zn ferrites using conventional standard ceramic technique. XRD patterns confirm the single phase cubic spinel structure up to x = 0.03 and appearance of a secondary phase of YFeO3for higher Y contents. FESEM images depict the distribution of grains and EDS spectra confirmed the absence of any unwanted element. Completion of solid state reaction and formation of spinel structure has been revealed from FTIR spectra. The FTIR data along with lattice constant, bulk density and porosity were further used to calculate the stiffness constant (Cij), elastic …
Numerous applications of hexagonal ferrites are related to their easy axis or easy plane magnetocrystalline anisotropy configurations. Certain W-type ferrites undergo spin reorientation transitions (SRT) between different anisotropy states on magnetic field or temperature variation. The transition point can be tuned by modifying the chemical composition, which suggests a potential application of hexaferrites in room temperature magnetic refrigeration. Here we present the results of structural and magnetic characterization of BaCo_xZn_{2-x}Fe_{16}O_{27} (0.7 \leq x \leq 2) doped barium ferrites…
NixMn0.25-xMg0.75Fe2O4 nano-ferrites (where x = 0.00, 0.05, 0.10, 0.15 and 0.20) were produced via sol-gel auto-combustion technique. Investigations were done into how the incorporation of Ni ions affects the Mn0.25Mg0.75Fe2O4 ferrite's structure, morphological, magnetic, and NO2 gas sensing features. All the samples are single-phase, based on the structural study utilizing the X-ray diffraction (XRD) pattern. In terms of the structure of the cubic spinel, according to the XRD study, the crystallite sizes range from 24.30 to 28.32 nm, indicating nano-crystallinity. The synthesis of spherical n…
Epitaxial thin film fabrication of iron oxides including magnetite Fe3O4 and epsilon-ferrite epsilon-Fe2O3 with the potential for advancing electromagnetic devices has been investigated, which led to the first ever epsilon-ferrite epitaxial layer being synthesized in the conventional sputtering process. Concerning Fe3O4 (100) / MgO (100) films, a cube-on-cube epitaxial relationship and sharp rocking curves with FWHM of 50 - 350 arcsec were confirmed regardless of the small amount of Ge additions. Sputtering Ar gas pressure PAr heavily influenced their magnetic and transport properties. High PA…
In this report we present results of magnetization measurements and investigation of aging and memory effect in bismuth ferrite multiferroic micro-cubes obtained by means of simple microwave synthesis procedure. It is found that difference between FC and ZFC magnetizations appears at the temperature of freezing of ferromagnetic domain walls. The decay of the magnetic moment vs. time described by power-law relation and the absence of memory effect indicate domain growth mechanism rather than the spin-glass phase.
