Magnetic Properties Of Nanomaterials Research Articles

A STRING MAGNETOMETER USING THE METHOD OF SMALL PERTURBATIONS

Subject and Purpose. The existing interest in nanosized magnetic materials requires equipment for express post-synthesis measurements of magnetic properties of these nanostructures in such a way as to exclude any mechanical displacement of the sample. Although there exist plenty of methods and devices for studying magnetic properties of materials, the development of novel schemes based on the known techniques for examining properties of magnetic nanomaterials, for example magnetic nanopowders, is a hot problem. Th e measurement equipment of the sort will detect changes in the magnetic properties of materials over time and under the infl uence of various factors, such as temperature, external magnetic fi elds, stabilizing substances. Method and Methodology. The developed setup for registering magnetic hysteresis loops is based on the method of small perturbations performed by an alternating magnetic fi eld. The devised scheme combines conventional physical principles of both hysterometers and vibrating-sample magnetometers. Results. With the aid of the developed setup, magnetic hysteresis loops of La 0.775 Sr 0.225 MnO3 nanopowder have been obtained and compared with the data provided by the well-known technique. A good agreement was observed. Th e measurement error was 10%. Conclusion. The suggested scheme can be used for the express registration of magnetic hysteresis loops of miscellaneous magnetic materials of various compositions, including nanoscale magnets.

Phase Transition of Fe₃O₄ Magnetic Material Based on Observation of Curie Temperature and Hysteresis Curve: Micromagnetic Simulation Study

Phase transition yesng happens to the material magnetite (Fe3O4) is an interesting phenomenon to study because it has many important applications, one of which is RAM (Radar Absorbing Material). The magnetic properties of nanomaterials are known to be influenced by their size. In this simulation research, the research objective was to analyze the temperature value of the Curie and the hysteresis curve of the Fe3O4 material with variations in the size of the material sample cube of 5 nm, 8 nm, 10 nm, 12 nm, and 15 nm. In this study, using a micromagnetic simulation method based on atomistic models with the Vampire program. The results showed that the Curie temperature value in the Fe3O4 material was influenced by variations in the size of the material. The Curie temperature values when the side sizes of the cube are 5 nm, 8 nm, 10 nm, 12 nm, and 15 nm, namely 650 K, 635 K, 650 K, 665 K and 645 K. The characteristics of the hysteresis curve for Fe3O4 material based on simulations at each material size (5 nm, 8 nm, 10 nm, 12 nm, and 15 nm) for several temperatures (0 K, 328 K, 473 K and 773 K) indicate that there is a change in the coercivity and field values. saturation.

Magnetic Nanomaterials: Chemical Design, Synthesis, and Potential Applications

Magnetic nanomaterials (MNMs) have attracted significant interest in the past few decades because of their unique properties such as superparamagnetism, which results from the influence of thermal energy on a ferromagnetic nanoparticle. In the superparamagnetic size regime, the moments of nanoparticles fluctuate as a result of thermal energy. To understand the fundamental behavior of superparamagnetism and develop relevant potential applications, various preparation routes have been explored to produce MNMs with desired properties and structures. However, some challenges remain for the preparation of well-defined magnetic nanostructures, including exchange-coupled nanomagnets, which are considered as the next generation of advanced magnets. In such a case, effective synthetic methods are required to achieve control over the chemical composition, size, and structure of MNMs. For instance, liquid-phase chemical syntheses, a set of emerging approaches to prepare various magnetic nanostructures, facilitate precise control over the nucleation and specific growth processes of nanomaterials with diverse structures. Among them, the high-temperature organic-phase method is an indispensable one in which the microstructures and physical/chemical properties of MNMs can be tuned by controlling the reaction conditions such as precursor, surfactant, or solvent amounts, reaction temperature or time, reaction atmosphere, etc. In this Account, we present an overview of our progress on the chemical synthesis of various MNMs, including monocomponent nanostructures (e.g., metals, metal alloys, metal oxides/carbides) and multicomponent nanostructures (heterostructures and exchange-coupled nanomagnets). We emphasize the high-temperature organic-phase synthetic method, on which we have been focused over the past decade. Notably, multicomponent nanostructures, obtained by growing or incorporating different functional components together, not only retain the functionalities of each single component but also possess synergic properties that emerge from interfacial coupling, with improved magnetic, optical, or catalytic features. Herein, potential applications of MNMs are covered in three representative areas: biomedicine, catalysis, and environmental purification. Regarding biomedicine, MNMs can detect or target biological entities after being modified with specific biomolecules, and they can be applied to magnetic resonance imaging, imaging-guided drug delivery, and photothermal therapy. Apart from their magnetic features, the catalytic performance of some MNMs resulting from their highly specific chemical components and surface structure will be briefly introduced, highlighting its impact in the methanol oxidation reaction, the oxygen reduction reaction, the oxygen and hydrogen evolution reactions, and the Fischer-Tropsch synthesis. Finally, environmental purification, primarily for water remediation, will be highlighted with two main aspects: the effective capture of bacteria and the removal of adverse ions in wastewater. We hope that this Account will clarify the progress on the controllable preparation of MNMs with specific compositions, sizes, and structures and generate broad interest in the realms of biomedicine and catalysis as well as in environmental issues and other potential applications.

Electroconductive and magnetic properties of pure carbon soot produced in arc discharge: Regimes of various buffer gas pressure

The electroconductive and magnetic properties of nanomaterials containing carbon nanoforms synthesised for electrocatalytic, electrochromic and ferrofluid applications, etc., are of interest to researchers. This article aims to understand the physical effects influencing the electroconductive and magnetic properties of materials synthesised by arc discharge. The nanomaterial formation processes leading to the formation of magnetic and electroconductive structures are also discussed. Arc discharge between graphitic electrodes results in the emergence of a fan‐shaped jet of helium and carbon. The gasdynamic and temperature parameters of the jet depend on the parameters of the arc discharge and the buffer gas. Variations in the parameters of the carbon vapour flow change the kinetics of carbon condensation, leading to variations in the morphology and structure of the carbon material. The main external parameter of the synthesis (buffer gas pressure) was varied in the study, and correlations between the intensity ratio of the D to G peaks on the Raman spectrum and the electrical conductivity and the magnetic susceptibility values were found. During the synthesis, nanographite structures were formed. However, the formation of an amorphous carbon structure on the free ‘zig‐zag’ edges of the graphite fragments reduced the magnetic susceptibility, the electrical conductivity and the ID/IG ratio.The amorphous carbon layer was deposited on the graphite structure, which reduces magnetic susceptibility, electrical conductivity and the ID/IG ratio.

Influence of Radiation-Induced Defects on Magnetic Properties of CoxNi1-xFe2O4 Nanomaterials

This paper presents the investigation of the probability of changes in the magnetic properties of nanomaterials in strong fields of charged particles, neutrons and gamma rays. CoxNi1-xFe2O4 nanoparticles were obtained by the hydrothermal method using polyethylene glycol. Investigation of the properties of this material showed that its magnetic properties depend on the concentration of Со2+. In this work it is shown that the nuclear reactions taking place in the crystal lattice sites can change the relative concentration of the components of test material and, accordingly, its magnetic properties, including the coercive force.

Methods of Synthesis of Nanodispersed Iron Oxides

The paper deals with the classification and analysis of main chemical methods of nanostructure iron oxide synthesis. Literature data are systematizated to select a universal method for revealing the relationship between the conditions of synthesis and structural, morphological and magnetic properties of nanomaterials.

Magnetic force microscopy study of shape engineered FEBID iron nanostructures

The capability to control matter down to the nanoscale level in combination with the novel magnetic properties of nanomaterials have attracted increasing attention in the last few decades due to their applications in magnetic sensing, hard disc data storage and logic devices. Therefore, many efforts have been devoted to the implementation of both nanofabrication methods as well as characterization of magnetic nanoelements. In this study, Fe‐based nanostructures have been synthesized on Si(100) by focused electron beam induced deposition (FEBID) utilizing iron pentacarbonyl as precursor. The so obtained nanostructures exhibit a remarkably high iron content (Fe > 80 at.%), expected to give rise to a ferromagnetic behaviour. For that reason, magnetic force microscopy (MFM) analyses were performed on the obtained FEBID Fe nanostructures. Moreover, object oriented micromagnetic framework (OOMMF) magnetic simulations have been executed to study the influence of the geometry on the magnetic properties of iron single‐domain nanowires. FEBID is a mask‐less nanofabrication method based on the injection of precursor gas molecules in proximity of the deposition area where their decomposition is locally induced by a focused electron beam.

DNA aptamer functionalized nanomaterials for intracellular analysis, cancer cell imaging and drug delivery

► DNA aptamer–nanomaterials combine unique optical or magnetic properties of nanomaterials with high selectivity of aptamers. ► Together they have enabled novel analytical techniques that advance our understanding of health and treatment of diseases. ► Recent work on using DNA aptamer–nanomaterials for analysis of intracellular components and metabolites are reviewed. ► Their recent applications in targeting and imaging of cancer cells and in cell-specific drug delivery are also highlighted.

FM-AFM crossover in vanadium oxide nanomaterials

The magnetic properties of nanomaterials based on vanadium oxide (multiwall nanotubes, nanorods, and nanolayers) have been investigated in the temperature range of 1.8–220 K by high-frequency (60-GHz) EPR. A transition from a ferromagnetic temperature dependence to an antiferromagnetic temperature dependence has been observed in nanorods and nanotubes with a decrease in the temperature. The FM-AFM crossover observed near TC ∼ 110 K is accompanied by a low-temperature increase in the Curie constant by a factor of 2.7–7. The comparison of the experimental data for various VOx nanoparticles indicates that the most probable cause of the change in the type of magnetic interaction is a change in the concentration of V4+ magnetic ions.

Electrical and magnetic properties of nanomaterials containing iron or cobalt nanoparticles

We have prepared nanocomposites consisting of narrowly sized metal-containing nanoparticles embedded in a polyethylene matrix and have established conditions for the fabrication of thick films and bulk materials from the synthesized polymer powders. Dielectric permittivity and resistivity measurements demonstrate that the electrical properties of the nanocomposites depend significantly on the nanoparticle size and content.The microwave absorption and permittivity of the materials are shown to vary little in a broad frequency range. The magnetization (including the remanent one) of the cobalt-containing nanomaterials is higher than that of the iron-containing samples.

The Synthesis and Properties of Magnetic Nanoparticles

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The Synthesis and Properties of Magnetic Nanoparticles

Magnetic nanoparticles are materials of great interest because of the remarkable fundamental properties exhibited by these materials as well as their technological potential in the area of biomedicine and other areas. The technologically useful properties of magnetic nanomaterials are not limited to their structural, chemical or mechanical behaviour, but also involve the phenomena that arise from their finite size and the surface effects that dominate the magnetic behaviour of individual nanoparticles. New techniques that have been developed recently have permitted researchers to produce larger quantities of nanomaterials and characterize them better. Here, some of the most promising procedures are reported, including techniques based on hydrothermal syntheses, sol-gel syntheses, co-precipitation syntheses, mechanochemical syntheses, sonochemical syntheses, spray pyrolysis and microemulsion-assisted syntheses.

Microstructure Characterization and Magnetic Properties of Nanomaterials

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Microstructure characterization and magnetic properties of nanomaterials

The microstructure and superparamagnetic properties of two systems of magnetic nano-particles are reviewed. A new type of magnetic core-shell Ni—Ce nanocomposite particle (15–50 nm) has been prepared. Typical HREM images and FFT patterns of HREM images showed that many planar defects (nanotwins and stacking faults) exist in the large Ni core zone (10–45 nm). The shell layers (3–5 nm) consist of an innermost Ni—Ce alloy and an outermost NiO oxide. FFT patterns from different regions of typical HREM images show well defined spots characteristic of core-shell nanocomposite materials. Magnetization measurements as a function of magnetic field and temperature showed that superparamagnetic behaviour is exhibited above the average block temperature (TB = 170 K). This superpara-magnetic relaxation was found to be modified by interparticle interactions that depend on the applied field and size distribution. In addition, antiferromagnetic order occurred with a Neél temperature TN of about 11 K. A spin-flip transition was observed below TN at a certain applied field. Novel carbon encapsulated Ni nanoparticles assemblies have been synthesized by modified arc-discharge under a methane atmosphere. The presence of carbon encapsulation is confirmed by HR-TEM lattice imaging, and nanodiffraction. The intimate and contiguous carbon fringe around these Ni nanoparticles is good evidence for complete encapsulation by carbon shell layers. Superparamagnetic property studies show that the blocking temperature TB is around 115K at 0.1 T applied field. Above TB, the magnetization M(H,T) can be described by the classical Langevin function L using the relation M/Ms(T = 0) = coth (μH/kT) — kT/μH. The particle size can be inferred from the Langevin fit (particle moment μ), which is a little larger than the HR-TEM observation. It is suggested that these assemblies of carbon encapsulated Ni nanoparticles have typical single-domain, field-dependent superparamagnetic relaxation properties, and this typical superparamagnetic behaviour is consistent with the Stoner—Wohlfarth theory of single-domain particles.

Fabrication and Properties of Nanosized Material Made by Using Colloidal Assemblies as Templates

Syntheses of nanosized particles by using colloidal assemblies as templates are described. It is shown that the chemical mechanism in nanoparticles production can differ in colloidal assemblies from those usually observed in homogeneous solution. Hence, the know how of the solution chemistry cannot always be transferred to collodal systems. The colloidal systems mimic nature to control size and shape of nanomaterials. It is possible to select the size and markodly reduce their distribution by a surface treatment of the nanoparticles. This favors formation of mono and multilayers made of nanoparticles. These particles form crystals organized in a three dimensional face-centered cubic superlattice. Optical and magnetic properties of nanomaterials are presented.