FMR study of 0.30(Fe

ZnO nanocrystals doped with Fe2O3 have been synthesized by the calcination method. Ferromagnetic resonance (FMR) study of 0.3(Fe2O3/0.7(ZnO) nanocomposite has been carried out in the 4–300 K range. The presence of magnetic zinc ferrite ZnFe2O4 nanoparticles with an average crystallite size of 11 nm was identified by XRD. Temperature dependence of the resonance field, linewidth and the integrate intensity calculated from FMR spectra has been determined. Existence of two temperature regimes: high (above 50 K) and low (below 50 K) has been established, further divided into two temperature ranges. The results of FMR study of agglomerated ZnFe2O4 nanoparticles indicate an important role of magnetic interactions, both inter-particle (exchange and dipolar) and intra-particle connected with the core-shell magnetic structure

Influence of an Electronic Structure of N-TiO2 on Its Photocatalytic Activity towards Decomposition of Acetaldehyde under UV and Fluorescent Lamps Irradiation

The electronic structure of N-TiO2 samples prepared by a sol-gel method was investigated by EPR (Electronic Paramagnetic Resonance) measurements and the energy-resolved distribution of electron traps. In EPR spectra, some of the resonance lines assigned to paramagnetic species of nitrogen and Ti3+ were detected. Sample prepared at 300 degrees C revealed the highest intensity line of the nitrogen paramagnetic centers, whereas that prepared at 400 degrees C showed a paramagnetic line for Ti3+. Measurements of the electron trap distribution showed higher density of electron traps for sample prepared at 400 degrees C than that at 300 degrees C. Sample prepared at 300 degrees C, which revealed the highest amount of nitrogen built in the titania in the interstitial position was the most active under visible light. It was evidenced that photocatalytic decomposition of acetaldehyde was dependent strongly on the BET surface area and electrokinetic potential of the photocatalyst surface. The UV content in the fluorescent lamp affected the yield of acetaldehyde decomposition

Magnetic frustration in lyonsite-type vanadates in FeVO

Six phases crystallizing in the lyonsite-type structure were synthesized by solid-state reaction between nFeVO4 and (1–n)Co3V2O8, where n = 0.73, 0.7143, 0.6667, 0.5843, 0.57, and 0.56. DC magnetic susceptibility in high-temperature range (T  > 100 K) was found to follow the Curie–Weiss law with negative and large value of the Curie–Weiss temperature. The effective magnetic moments were slightly bigger than for high-spin Co2+ and Fe3+ ions. Spin-glass-like features observed in magnetic FC/ZFC susceptibilities at low temperatures (T  < 15 K) could be the result of a huge magnetocrystalline anisotropy of randomly oriented crystallites or magnetic nanoclusters in the powder samples, or they could be due to magnetic frustration arising from competition of ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. The presence of FM component with a large coercive field and strong magnetic remanence in samples with large Co content was evidenced at low temperature. Weak and very broad electron paramagnetic resonance (EPR) spectra were analyzed by decomposition on Lorentzian components and were attributed to magnetic spin clusters or metallic precipitates not involved in bulk magnetism registered in magnetization measurements. In addition, for n = 0.7143, 0.6667 samples, the much narrower line was due to the V4+ magnetic defects connected with oxygen vacancies

Magnetic study of Fe

Nanocomposites of Fe3O4 nanoparticles (NPs) impregnated with silver NPs display antibacterial properties and may be used in water treatment as disinfection agent. Three samples were synthesized: Fe3O4 NPs obtained by the precipitation method and additionally two samples with added silver NPs with mass ratio of Ag:Fe3O4 equal to 1:100 and 2:100. Magnetic properties of these samples were studied by SQUID magnetometry (in temperature range 2–300 K and magnetic fields up to 70 kG) and magnetic resonance technique at RT. Temperature dependence of dc susceptibility revealed the blocking temperature close to RT in all three samples and allowed to determine the presence of single or multi-mode distribution of NP sizes in a particular sample. Isothermal magnetisation measurements showed that the presence of silver NPs, especially those with smaller sizes, decreases the saturation magnetisation. The shape of ferromagnetic loop registered at T = 2 K was used to discuss the sizes of NP magnetic clusters in our samples. Conclusions obtained from analysis of the ferromagnetic resonance spectra were consistent with the propositions based on the magnetometric studies

On the characteristic and stability of iron diet supplements

The iron diet supplements: AproFER 1000 and AproTHEM were subjected to various chemical, microbial and magnetic analysis. The microbial analysis revealed no presence of pathogenic bacteria in the studied products. No significant changes in iron content or forms (bivalent/trivalent) were observed in EPR analysis of supplements stored at different conditions for a long period of time. The chemical and magnetic analysis showed that both AproFER 1000 and AproTHEM contain a high concentration of bivalent iron so they can be used as an iron diet supplements

Magnetic resonance study of co-modified (Co,N)-TiO2 nanocomposites

Three nCo,N-TiO2 nanocomposites (where cobalt concentration index n = 1, 5 and 10 wt %) were prepared and investigated by magnetic resonance spectroscopy at room temperature. Ferromagnetic resonance (FMR) lines of magnetic cobalt agglomerated nanoparticle were dominant in all registered spectra. The relaxation processes and magnetic anisotropy of the investigated spin system essentially depended on the concentration of cobalt ions. It is suggested that the samples contained two magnetic types of sublattices forming a strongly correlated spin system. It is suggested that the existence of strongly correlated magnetic system has an essential influence of the photocatalytic properties of the studied nanocomposites

Magnetic properties of co-modified Fe,N-TiO2 nanocomposites

Iron and nitrogen co-modified titanium dioxide nanocomposites, nFe,N-TiO2 (where n = 1, 5 and 10 wt% of Fe), were investigated by detailed dc susceptibility and magnetization measurements. Different kinds of magnetic interactions were evidenced depending essentially on iron loading of TiO2. The coexistence of superparamagnetic, paramagnetic and ferromagnetic phases was identified at high temperatures. Strong antiferromagnetic interactions were observed below 50 K, where some part of the nanocomposite entered into a long range antiferromagnetic ordering. Antiferromagnetic interactions were attributed to the magnetic agglomerates of iron-based and trivalent iron ions in FeTiO3 phase,whereas ferromagnetic interactions stemmed from the F-center mediated bound magnetic polarons

DC magnetization of titania supported on reduced graphene oxide flakes

DC magnetization of a series of titania nano-composites modified with reduced graphene oxide (rGO) has been investigated. Hysteresis loops observed at room temperature disappeared at low temperatures. At a temperature of about 100 K, a phase transition to the super-ferromagnetic order state was observed, probably due to the linear expansion and self-reorientation of the magnetic moments. Processes associated with magnetic moment reorientation can cause a hysteresis loop to disappear at low temperatures as well as superferromagnetic ordering. It was suggested that the isolated nanoparticle in the nanopore could be used to create a “compass” at a nanometer-sized level that would be many times more sensitive than the conventional one. Measurements of the zero-field cooling and field cooling modes do not exclude the possibility of the coexistence of a superparamagnetic state