Strong Magnetic Properties Research Articles

Structural and magnetic properties of the layered manganese oxychalcogenides (LaO)2Mn2Se2O and (BaF)2Mn2Se2O

The new layered manganese oxychalcogenides (LaO)$_2$Mn$_2$Se$_2$O and (BaF)$_2$Mn$_2$Se$_2$O, isostructural to (LaO)$_2$Fe$_2$Se$_2$O, were synthesized by using solid state reaction. The single crystals of former compound were also successfully grown by using high temperature fusion method. The polycrytalline samples showed the insulating behavior, with the activation energy gaps of about 278 meV and 416 meV for (LaO)$_2$Mn$_2$Se$_2$O and (BaF)$_2$Mn$_2$Se$_2$O, respectively. The magnetic susceptibility indicated an antiferromagnetic (AFM) transition at around 160K and strong anisotropic magnetic properties below T$_N$ for the former compound, which suggests a long-range canted AFM ordering. A broad maximum of the susceptibility can be observed for the two compound at high temperatures, say 360 K and 210 K respectively, suggesting that strong magnetic correlation gives rise to low-dimensional AFM or short-range ordering at high temperatures in these rare transition metal oxychalcogenides with a frustrated AFM checkerboard spin lattice.

Drops deformation and magnetic permeability of a ferrofluid emulsion

In the paper the novel soft magnetic composite system is investigated. A ferrofluid emulsion studied demonstrates the strong magnetic properties which are atypical for commonly known emulsions. Interaction of ferrofluid emulsions with a magnetic field is considered. Structural transformations in these media, such as deformation of emulsion microdroplets and emulsion inversion, are studied. The changes in the relative permeability of emulsion associated with structural transformations are investigated. The theory of the observed phenomena is developed, and the feasibility of effectively controlling the magnetic properties of ferrofluid emulsions by applying a magnetic field is demonstrated.

The Dilute Magnetic and Optical Properties of Mn-Doped ZnO Nanowires

We present a study of the dilute magnetic and optical properties of Mn-doped ZnO nanowires (Nws) fabricated by means of a liquid phase evaporation deposition process. The samples were grown using a mixed Zn/Mn liquid source with a mol ratio of Mn 10% in a constant O2/Ar gas at 580°C. The nanowires show a strong UV emission at 405 nm and a blue emission at 433 nm in the photoluminescence spectrum. In addition, they present a strong reversible smooth ferromagnetic hysteresis loop at room temperature, and the corresponding saturation magnetization Msis up to 0.015 emu/g Oe, showing that the nanowires are of a ferromagnetism semiconductor (DMS). With the strong magnetic and photoluminescence properties, ZnO : Mn Nws will be used in fields of making electromagnetic devices and magneto-optical storage devices.

Magnetic colloidosomes fabricated by Fe3O4–SiO2 hetero-nanorods

Magnetic colloidosomes were fabricated by directing self-assembly of magnetic-mesoporous hetero-nanorods at the interface of water-in-oil droplets. Emulsions stabilized by the adsorbed particles without any surfactant indicate that such rod-like nanoparticles have specific advantages in making stable and intact shells than spherical particles. The integrity and emulsion stability of the colloidosomes were strongly influenced by the geometric shape of the hetero-nanorods. The optimum length of the nanorods to construct the colloidosomes was studied and demonstrated. The as-formed magnetic colloidosomes can exhibit unique encapsulation behaviors and show strong magnetic response properties, which will find huge potential application in multicompartment reactor, drug delivery and other biomedical fields.

Photoluminescent Fe 3O 4/carbon nanocomposite with magnetic property

Fe 3O 4/carbon nanocomposite has been prepared by a facile chemical method, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy and scanning electron microscopy. The fluorescent and magnetic properties of the sample were investigated by fluorescence spectroscopy and vibrating-sample magnetometer, respectively. The results indicate that the Fe 3O 4/carbon nanocomposite exhibit good photoluminescent (emission ranging from 425 to 550 nm) and strong magnetic (saturation magnetization of 44.2 emu/g) properties.

Effect of Dy additive on microstructure and magnetic propertiesof rapidly solidified Nd-Fe-B strips

Sintered Nd-Fe-B magnets made from strip cast alloys have been studied extensively owing to their strong permanent magnetic properties. Up to now the studies mainly focus on technology parameters of strip casting, including casting temperature, wheel speed and phase transition temperature and so on. However, microstructure and properties of rapidly solidified strips could be influenced by the composition of alloy. In this work, the effects of added Dy element on microstructures and properties of Nd-Fe-B rapidly solidified strips have been investigated. The strips shad a pronounced texture of the tetragonal T1(2 ∶14 ∶1) phase as shown by the prominent (00l) peaks at wheel surface. The alignment coefficient of the strips was the highest when Dy content ranged from 1 to 2at%. This is the result of the microstructure of strips being optimized through an appropriate amount of Dy addition. At the same time, the volume fraction of isotropic crystal decreased as Dy content increased. It revealed that the oxidation speed decreased with increasing Dy content.

Facile Synthesis of Ultrasmall and Hexagonal NaGdF4: Yb3+, Er3+ Nanoparticles with Magnetic and Upconversion Imaging Properties

Synthesis of nanomaterials with multi-imaging modality is of great importance in clinical molecular imaging and diagnostics. This work reports novel synthetic strategy to create ultrasmall and hexagonal upconversion nanoparticles (UCNPs), β-NaGdF4: Yb3+, Er3+, and β-NaGdF4: Yb3+, Tm3+, with inherent magnetic and efficient upconversion properties. The use of new combination of lanthanide chloride and sodium TFA as the precursors for UCNPs gave the best results in terms of size (10−40 nm), crystallinity and morphology, and proved to be cost- and time-saving. Water solubilization of both NaGdF4: Yb3+, Er3+, and β-NaGdF4: Yb3+, Tm3+ UCNPs was achieved by homogeneous polymer coating using amphiphilic poly(acrylic acid) derivatives. The strong upconversion and magnetic properties were maintained after extensive polymer coating process. To see the potential of the UCNPs for biological applications, the surface of NaGdF4: Yb3+, Er3+ UCNPs were functionalized with Ni-nitrilotriacetate (NiNTA) moiety. The remarkabl...

Reconnaissance investigations of magnetic susceptibility of subsoil formation in the selected areas in southern Poland

In the article, the reconnaissance investigations of the magnetic susceptibility of soils and ochre are presented. Field investigations have been performed in southern Poland; namely in the Łąki Nowohuckie area of Krakow, the eastern surroundings of the city of Trzebinia, and the hamlet of Czerwonki near Rzeszow. Laboratory magnetic analyses have been completed. An increase of soil susceptibility has been observed in the studied areas with high anthropopression (Krakow and Trzebinia). It has been proven that iron particles collected in the soil come from urban-industrial emissions. The higher susceptibility of soils in the Łąki Nowohuckie area, than in the vicinity of Trzebinia, has also been affirmed. The diversity of the low values of soil susceptibility in the Trzebinia area is not connected to the Zn-Pb ores which occurred there. The investigations of ochre susceptibility at Czerwonki Hermanowskie have confirmed its quite strong magnetic properties in comparison with properties of the soil situated in a nearby deposit. The large differentiation of ochre susceptibility has been observed. It is probably connected with the mineral composition of ochre and the processes that occurred in the deposit. The ochre deposit slightly disturbs the geomagnetic field (microanomalies) as is shown on the micromagnetic anomaly map.

Preparation, Characterization, and Application of Magnetic Fe-SBA-15 Mesoporous Silica Molecular Sieves

Magnetic Fe-SBA-15 mesoporous silica molecular sieves were prepared, characterized, and used for magnetic separation. Wet impregnation, drying, and calcination steps led to iron inclusion within the mesopores. Iron oxide was reduced to the metal form with hydrogen, and the magnetic Fe-SBA-15 was obtained. Fourier-transform infrared spectroscopy confirmed the preparation process from the oxide to metal forms. The structure of magnetic materials was confirmed by Mössbauer spectra. Powder X-ray diffraction data indicated that the structure of Fe-SBA-15 retained the host SBA-15 structure. Brunauer-Emmett-Teller analysis revealed a decrease in surface area and pore size, indicating Fe-SBA-15 coating on the inner surfaces. Scanning electron micrographs confirmed the decrease in size for modified SBA-15 particles. From scanning electron micrographs, it was found that the size of the modified SBA-15 particles decreased. Transmission electron micrographs also confirmed that modified SBA-15 retained the structure of the parent SBA-15 silica. Fe-SBA-15 exhibited strong magnetic properties, with a magnetization value of 8.8 emu g−1. The iron content in Fe-SBA-15 was determined by atom adsorption spectroscopy. Fe-SBA-15 was successfully used for the magnetic separation of three aromatic compounds in water. Our results suggest wide applicability of Fe-SBA-15 magnetic materials for the rapid and efficient separation of various compounds.

High-temperature ferromagnetism by means of oriented nanocolumns: Co clustering in (Zn,Co)O

In order to provide insight into the magnetic properties of semiconductors with ferromagnetic inclusions, we present a thorough quantitative analysis of (Zn,Co)O films with high Co concentration, which give rise to high saturation magnetization values (similar to 110 kA m(-1)) at room temperature. From the orientation-, temperature-, and field-dependent responses of the magnetization and of the Q-band ferromagnetic resonance modes, we give evidence of two types of nanosized ferromagnetic Co clusters and derive their respective contributions. The first type are spherical with diameters about 5 nm and blocking temperatures T(B) about 100 K. The second type are elongated along the surface normal and crystallographically oriented with respect to the ZnO host. Some are nanocolumns about 4 nm wide, whose height may reach up to 60 nm, leading to T(B) >= 300 K. These results are confirmed by high-resolution transmission electron microscopy analysis. In addition to provide transition from ferromagnetism to superparamagnetism above 300 K, the nanocolumns lead to strong anisotropic magnetic properties. We believe that they could find applications in spintronic devices.

Structure and multiferroic properties of BiFeO 3 powders

Bismuth ferrite powders were synthesized by a simple sol–gel method at the temperature as low as 450 °C. Single phase BiFeO 3 powders with a rhombohedral perovskite structure were fabricated after Bi–Fe gels were calcined at 450–650 °C. Atomic ratio of Bi to Fe is approximately 1:1 for BiFeO 3 powders, as determined by energy dispersive X-ray spectrometer. BiFeO 3 powders show weak ferromagnetism at room temperature and strong size-dependent magnetic properties, which is different from the linear M– H relationship in BiFeO 3 ceramics. Dielectric anomaly at round 330 °C near the magnetic transition point corresponds to the antiferromagnetic to paramagnetic phase transition, indicating the coupling between polarization and magnetization in BiFeO 3 powders. A reversible ferroelectric phase transformation of BiFeO 3 powders has been detected at 827 °C by a differential thermal analysis.

Synthesis, characterization and application of magnetic-zirconia nanocomposites

In the present study, a magnetic-zirconia nanocomposite was successfully synthesized by a single-step co-precipitation method. The as-prepared nanocomposite was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and nitrogen sorption measurements. The ultimate material was found to be Fe3O4–ZrO2 nanoparticles with average diameter of 80 nm, high surface area up to 166 m2/g, and strong magnetic property. The application of this new nanocomposite was herein demonstrated by the adsorption of ethyl methylphosphonic acid, a degradation product of nerve agent in water, followed by mass spectrometry detection. Excellent adsorption could be observed, indicating the as-synthesized material was effective to remove phosphonic acid compound from water. Apart from adsorption, the Fe3O4–ZrO2 nanocomposite is promising in various applications such as catalysis and bioseparation.

Novel One-Pot Synthesis of Magnetite Latex Nanoparticles by Ultrasound Irradiation

A simple and efficacious procedure for the synthesis of magnetite nanoparticles has been achieved via a sonochemical miniemulsion polymerization process. The sonochemically synthesized magnetite encapsulated polymer latex particles exhibit excellent colloidal stability and strong magnetic properties, and are of a size that makes them technologically relevant. This novel method may be readily extended to the preparation of multiple combinations of different polymers and encapsulated materials.

Characterization of Novel Chip Temperature-Sensing Device Using Mn-Substituted Li–Zn–Cu Ferrite

It has been very difficult to develop a miniaturized temperature sensor device using the conventional temperature-sensitive ferrites, such as Mn-Zn ferrite, which is due to difficulty of the high-frequency operation, because of their low natural resonance frequency (below 1 MHz) and low electrical resistivity (around 102-104 Omegamiddot cm). The authors have recently developed a polycrystalline Mn-substituted Li-Zn-Cu ferrite with a high natural resonance frequency beyond 10 MHz and high resistivity over 106 Omegamiddot cm, which exhibited strong temperature-dependent magnetic properties. It was considered that the transmission-line device using a new temperature-sensitive ferrite as an electromagnetic-field propagation substrate enables us to obtain a novel chip temperature-sensing micro device, because of the possibility of high-frequency operation due to a high resonance frequency and high resistivity of the new ferrite. We have simulated a quarter-wavelength resonator using the Mn-substituted Li-Zn-Cu ferrite substrate and its temperature-dependent properties. Since the quarter-wavelength transmission-line resonator includes distributed inductance and capacitance depending on the temperature-sensitive electromagnetic property of the ferrite substrate, this type of device operates as an integrated LC resonator-type temperature sensor. In this study, the integrated resonator-type temperature sensor using a spiral strip-line structure with the Mn-substituted Li-Zn-Cu ferrite substrate was fabricated, and its temperature-dependent characteristics were evaluated.

Angle Difference Between $B$ vector and $H$ Vector in Anisotropic Electrical Steel

The numerical model following the equivalent magnetic domain method is proposed to calculate the anisotropy of the magnetic properties of electrical steel. The angle difference between magnetic flux density vector and magnetic field vector, which is observed in the measurement data, is clearly expressed by the proposed model. The angles characteristics of stepwise or lamped shape are shown to be consequences of the strong magnetic anisotropic property.

Efficient Removal of Cr(VI) from Aqueous Solution with Fe@Fe2O3 Core−Shell Nanowires

The batch removal of Cr(VI) from simulated wastewater with Fe@Fe2O3 core-shell nanowires (FCSNs) was investigated in this study. Itwas found that each gram of the FCSNs could remove 7.78 mg of Cr(VI) from simulated wastewater containing 8.0 mg L(-1) of Cr(VI) with an initial pH of 6.5 at room temperature. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Cr(VI) removal was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared and Cr(VI)-adsorbed FCSNs were carefully examined by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopic analysis (XPS). The characterization results suggested that the adsorbed Cr(VI) was partially reduced to Cr(lll) in Cr2O3/Cr(OH)3 on the FCSNs. The possible mechanism of removal of Cr(VI) on FCSNs was proposed, which involved the dominant Cr(VI) adsorption, followed by the partial reduction of Cr(VI) to Cr(III) (chromium(III) oxyhydroides) on the surface of FCSNs. These Fe@Fe2O3 core-shell nanowires with high specific surface area and strong magnetic property are very attractive for the removal of Cr(VI) from wastewater.

Preparation of hybrid polymer nanocomposite microparticles by a nanoparticle stabilised dispersion polymerisation

We report the use of nanoparticles to stabilise free radical dispersion polymerisations, without the need for any conventional stabiliser, leading to the preparation of polystyrene nanocomposites. The products are well characterised spherical polymer microparticles decorated with nanoparticles on their surfaces. In this paper we demonstrate the process with Fe3O4nanoparticles yielding a product with a strong magnetic property. By using this in situpolymerisation technique, not only can nanoparticles in aqueous solution be harvested, but also this provides a completely new route to polymer composites. Thus, functional nanoparticles can be immobilised onto the surface of the polymer beads to modify significantly their properties.

Fe<SUB>74.5−<I>x</I></SUB>Cu<I><SUB>x</SUB></I>V<SUB>3</SUB>Si<SUB>13.5</SUB>B<SUB>9</SUB> as-Spun Ribbons Prepared by Melt-Spinning Technique

Fe-Cu-V-Si-B nanocrystalline ribbons can be prepared using a melt-spinning technique without annealing processes. An appropriate addition of Cu improves the nucleation of α-Fe(Si) in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons. There is an optimal Cu content, about x=2.5, for obtaining largest permeability and lowest magnetostriction in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons. The permeability value (about 2.4×104) of as-spun Fe72Cu2.5V3Si13.5B9 (x=2.5) is much larger than that of Fe73.5Cu1V3Si13.5B9 annealed ribbons, due to the grain size of α-Fe(Si) for the former (12 nm) smaller than the later (41 nm). The smaller grain size of α-Fe(Si) for as-spun ribbon Fe72Cu2.5V3Si13.5B9 may be attributed to the refinement effect of Cu and the effect of high wheel speed in melt-spinning processes. Meanwhile, we have suggested that the capability of an element expelled from α-Fe(Si) and partitioned in the remaining amorphous phase is connected with the refinement of α-Fe(Si) grains. Based on Darken-Gurry solid solubility model, we have derived that the grain size of α-Fe(Si) reduces in order of Ta > Nb > Mo > W > V > Cr, which agrees to the experimental data very well. In addition, the DO3 ordered superstructure of α-Fe(Si) is observed in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons, however it seems that the ordered degree of α-Fe(Si) grain is not a criterion for obtaining strong soft magnetic properties.

多結晶Li-Zn-Cuフェライトの感温性に及ぼすLiフェライトの影響

Mn-substituted Li-Zn-Cu ferrite polycrystal is known to be a high-frequency ferrite. The authors recently clarified that this ferrite exhibits strong temperature-dependent magnetic properties. To our knowledge, detailed information on the temperature dependence of this new temperature-sensitive ferrite has not been reported. In the present study, several polycrystalline ferrites were fabricated while controlling the Li-ferrite content to investigate the chemical composition dependence of the temperature characteristics of their magnetic properties. As a result, it was clarified that the strong temperature sensitivity of the Li-Zn-Cu ferrite depended on the large temperature coefficient of the anisotropy constant of Li-ferrite. In addition, the smaller Li-ferrite content intensified the temperature dependence of the apparent anisotropy field, hence reinforcing the temperature-dependent magnetic properties.

Quasi-quartet crystal electric field ground state in a tetragonal [formula omitted] single crystal

We have successfully grown the single crystals of CeAg 2 Ge 2 , for the first time, by flux method and studied the anisotropic physical properties by measuring the electrical resistivity, magnetic susceptibility and specific heat. We found that CeAg 2 Ge 2 undergoes an antiferromagnetic transition at T N = 4.6 K . The electrical resistivity and susceptibility data reveal strong anisotropic magnetic properties. The magnetization measured at T = 2 K exhibited two metamagnetic transitions at H m 1 = 31 kOe and H m 2 = 44.7 kOe , for H ∥ [1 0 0] with a saturation magnetization of 1.6 μ B / Ce . The crystalline electric field (CEF) analysis of the inverse susceptibility data reveals that the ground state and the first excited states of CeAg 2 Ge 2 are closely spaced indicating a quasi-quartet ground state. The specific heat data lend further support to the presence of closely spaced energy levels.