Showing papers on "Saturation (magnetic) published in 2008"
TL;DR: The first observation of saturating transistor characteristics in a graphene field-effect transistor is reported, demonstrating the feasibility of two-dimensional graphene devices for analogue and radio-frequency circuit applications without the need for bandgap engineering.
Abstract: The first observation of saturating transistor characteristics in a graphene field-effect transistor is reported. The saturation velocity is attributed to scattering by interfacial phonons in the silicon dioxide layer supporting the graphene channels. These results demonstrate the feasibility of graphene devices for analogue and radio-frequency circuit applications without the need for bandgap engineering.
1,600 citations
TL;DR: In this paper, the magnetostriction of the MRE consisting of carbonyl iron particles displaced in the matrix made of a silicone rubber was measured by strain gauge and the mechanism of magnetostrictive effect of the composite was proposed to explain the phenomenon.
214 citations
TL;DR: In this article, the properties of water and their changes under the action of a magnetic field were gathered by the spectrum techniques of infrared, Raman, visible, ultraviolet and X-ray lights, which may give an insight into molecular and atomic structures of water.
Abstract: The properties of water and their changes under the action of a magnetic field were gathered by the spectrum techniques of infrared, Raman, visible, ultraviolet and X-ray lights, which may give an insight into molecular and atomic structures of water. It was found that some properties of water were changed, and a lot of new and strange phenomena were discovered after magnetization. Magnetized water really has magnetism, which has been verified by a peak shift of X-ray diffraction of magnetized water + Fe(3)O(4) hybrid relative to that of pure water + Fe(3)O(4) hybrid, that is a saturation and memory effect. The properties of infrared and ultraviolet absorptions, Raman scattering and X-ray diffraction of magnetized water were greatly changed relative to those of pure water; their strengths of peaks were all increased, the frequencies of some peaks did also shift, and some new peaks, for example, at 5198, 8050 and 9340 cm(-1), occurred at 25 degrees C after water was magnetized. In the meanwhile, the magnetized effects of water are related to the magnetized time, the intensity of an externally applied magnetic field, and the temperature of water, but they are not a linear relationship. The study also showed a lot of new and unusual properties of magnetized water, for example, the six peaks in 3000-3800 cm(-1) in infrared absorption, the exponential increase of ultraviolet absorption of wave with the decreasing wavelength of light of 200-300 nm, the frequency-shifts of peaks, a strange irreversible effect in the increasing and decreasing processes, as well as a stronger peak of absorption occurring at 50 degrees C, 70 degrees C and 80 degrees C, the existence of many models of motion from 85 degrees C to 95 degrees C in 8000-10000 cm(-1), and so on. These results show that the molecular structure of water is very complicated, which needs further study. Furthermore, the macroscopic feature of mechanics, for instance, surface tension force of magnetized water, was also measured. Experiments discovered that the size in contact angles of magnetized water on the surface of hydrophobic materials decreases, thus the surface tension force of magnetized water decreases relative to that of pure water. It is seen from the above results that the clustering structure of hydrogen-bonded chains and polarization effects of water molecules are enhanced after magnetization. These results are helpful in revealing the mechanism of magnetization of water.
188 citations
TL;DR: In this paper, the magnetic properties of piezoelectric actuators are investigated at room temperature as a function of the voltage controlled stress exerted by the actuator on the Ni film.
Abstract: The control of magnetic properties by means of an electric field is an important aspect in magnetism and magnetoelectronics. We here utilize magnetoelastic coupling in ferromagnetic/piezoelectric hybrids to realize a voltage control of magnetization orientation at room temperature. The samples consist of polycrystalline nickel thin films evaporated onto piezoelectric actuators. The magnetic properties of these multifunctional hybrids are investigated at room temperature as a function of the voltage controlled stress exerted by the actuator on the Ni film. Ferromagnetic resonance spectroscopy shows that the magnetic easy axis in the Ni film plane is rotated by 90 degree upon changing the polarity of the voltage Vp applied to the actuator. In other words, the in-plane uniaxial magnetic anisotropy of the Ni film can be inverted via the application of an appropriate voltage Vp. Using SQUID magnetometry, the evolution of the magnetization vector is recorded as a function of Vp and of the external magnetic field. Changing Vp allows to reversibly adjust the magnetization orientation in the Ni film plane within a range of approximately 70 degree. All magnetometry data can be quantitatively understood in terms of the magnetic free energy determined from the ferromagnetic resonance experiments. These results demonstrate that magnetoelastic coupling in hybrid structures indeed is a viable option to control magnetization orientation in technologically relevant ferromagnetic thin films at room temperature.
158 citations
TL;DR: In this article, the authors present results of two-and three-dimensional particle-in-cell simulations of magnetic turbulence production by isotropic cosmic-ray ions drifting upstream of supernova remnant shocks.
Abstract: We present results of two- and three-dimensional particle-in-cell simulations of magnetic turbulence production by isotropic cosmic-ray ions drifting upstream of supernova remnant shocks. The studies aim at testing recent predictions of a strong amplification of short-wavelength magnetic field and at studying the subsequent evolution of the magnetic turbulence and its back-reaction on cosmic-ray trajectories. For our parameters an oblique filamentary mode grows more rapidly than nonresonant parallel modes analytically found in the limit -->? ?i, and the growth rate is slower than is estimated for the parallel plane wave mode. The evolved oblique filamentary mode was also observed in MHD simulations to dominate in the nonlinear phase, when the structures are already isotropic. We thus confirm the generation of the turbulent magnetic field due to the drift of cosmic-ray ions in the upstream plasma, but as our main result find that the amplitude of the turbulence saturates at about -->?B/B ~ 1. The back-reaction of the magnetic turbulence on the particles leads to an alignment of the bulk flow velocities of the cosmic rays and the background medium, which accounts for the saturation of the instability at moderate amplitudes of the magnetic field. Previously published MHD simulations have assumed a constant cosmic-ray current and no energy or momentum flux in the cosmic rays, which excludes a back-reaction of the generated magnetic field on cosmic rays, and thus the saturation of the field amplitude is artificially suppressed. This may explain the continued growth of the magnetic field in the MHD simulations. A strong magnetic field amplification to amplitudes -->?B B0 has not been demonstrated yet.
148 citations
TL;DR: Spinel ferrite, MFe 2O 4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol-gel technology and can potentially be used in micro/nano electronic devices, gas-sensors, and catalysts.
Abstract: Spinel ferrite, MFe2O4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol−gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts. The ribbons exhibited weak saturation magnetizations and low coercivities at room temperature, but at low temperature, saturation magnetizations and coercivities increased a lot, especially for CoFe2O4 ribbons, reaching 72 emu/g and 1.45 T at 2 k, respectively. These novel magnetic ribbons can potentially be used in micro/nano electronic devices, gas-sensors, and catalysts.
126 citations
TL;DR: In this article, the structure of Eurofer 97 has been determined by diffraction and electron microscopy techniques and the magnetic, electrical and thermal properties of the steel have been reported in the temperature range from room temperature up to 900 K. The experimental data are described by empirical equations and are compared with data from similar steel alloys.
125 citations
TL;DR: In this article, the effects of increasing the magnetic thickness on the permeability spectra were measured and modeled, and the effect of magnetic vias and elongated structures on the inductors were examined.
Abstract: On-chip inductors with magnetic material are integrated into both advanced 130 and 90 nm complementary metal-oxide semiconductor processes. The inductors use aluminum or copper metallization and amorphous CoZrTa magnetic material. Increases in inductance of up to 28 times corresponding to inductance densities of up to 1.3 μ H / mm 2 were obtained, significantly greater than prior values for on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. The CoZrTa was chosen for its good combination of high permeability, good high-temperature stability ( > 250 ° C ) , high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The CoZrTa alloy can operate at frequencies up to 9.8 GHz , but trade-offs exist between frequency, inductance, and quality factor. The effects of increasing the magnetic thickness on the permeability spectra were measured and modeled. The inductors use magnetic vias and elongated structures to take advantage of the uniaxial magnetic anisotropy. Techniques are presented to extract a sheet inductance and examine the effects of magnetic vias on the inductors. The inductors with thick copper and thicker magnetic films have resistances as low as 0.04 Ω , and quality factors up to 8 at frequencies as low as 40 MHz.
120 citations
TL;DR: The results of this study can be exploited for the rational design of MRI contrast agents, based on lanthanide oxide particles, with high efficiencies at magnetic field strengths of more than 1.5 T.
Abstract: The transverse 1H relaxivities of aqueous colloidal solutions of dextran coated Dy2O3 nanoparticles of different sizes were investigated at magnetic field strengths (B) between 7 and 17.6 T. The particle size with the maximum relaxivity (r2) appears to vary between 70 nm at 7 T (r2 ≈ 190 s−1 mM−1) and 60 nm at 17.6 T (r2 ≈ 675 s−1 mM−1). A small difference between r2 and r2∗ was observed, which was ascribed to the effect of the dextran coating. The value of r2 is proportional to B2 up to 12 T after which it saturates. Independent magnetization measurements on these particles at room temperature at magnetic field strengths up to 30 T, however, show a typical paramagnetic behavior with a magnetization of the particle that is proportional to the field strength. The saturation in the curve of r2 as a function of B2 was tentatively explained by the presence of an extremely fast relaxing component of the signal at high field strengths, which is not observable on the NMR time scale. The results of this study can...
113 citations
TL;DR: In this article, the preparation of nanocrystalline Fe-Ni powders by mechanical alloying method, which can be used in soft magnetic composites, was discussed, and it was found that higher milling time resulted in larger lattice parameter, higher microstrains and smaller crystallite sizes.
97 citations
TL;DR: The average diameter of a single particle (core plus dextran) is 92 ± 14 nm as measured by photon correlation spectroscopy as mentioned in this paper, and the long-range collective magnetic behavior appears to play a major role in enhancing the SAR.
Abstract: Magnetic nanoparticles with a high specific absorption rate (SAR) have been developed and used in mouse models of cancer. The magnetic nanoparticles are comprised of predominantly iron oxide magnetic cores surrounded by a dextran layer for colloidal stability. The average diameter of a single particle (core plus dextran) is 92 ± 14 nm as measured by photon correlation spectroscopy. Small angle neutron scattering measurements under several H 2 O ∕ D 2 O contrast conditions and at varying nanoparticle concentrations have revealed three length scales: > 10 μ m , several hundred nanometers, and tens of nanometers. The latter corresponds to the particle diameter; the several hundred nanometers corresponds to a hard sphere interaction radius of the core/shell nanoparticles; > 10 μ m corresponds to the formation of long-range, many-particle structures held together by magnetic interactions and dextran. The long-range collective magnetic behavior appears to play a major role in enhancing the SAR. For samples having nominally equal concentrations and similar saturation magnetizations, the measured SAR is 1075 W /(g of Fe) for tightly associated nanoparticles and 150 W /(g of Fe) for very loosely associated nanoparticles at an applied field of 86 kA ∕ m ( 1080 Oe ) and 150 kHz .
TL;DR: In this paper, an annular-shaped axis-encircling electron beam using a smooth magnetic cusp was studied through numerical simulations and experiments for harmonic operation of a gyrodevice.
Abstract: The generation of an annular-shaped axis-encircling electron beam using a smooth magnetic cusp was studied through numerical simulations and experiments for harmonic operation of a gyrodevice. Two magnetic coils were used to form a magnetic cusp located just downstream from the velvet cathode of an accelerator diode. An electron beam of current 34 A and voltage 130 kV with an adjustable velocity ratio α up to 1.2 was fully transported to the downstream uniform magnetic field region and used to drive a gyrotron traveling wave amplifier into saturation.
Patent•
HGST1
TL;DR: In this article, a thin film perpendicular magnetic head with a narrow main pole capable of a high recording density in excess of 100 gigabits per square inch and generating a high magnetic recording field, while also being modified to suppress remanent magnetic fields occurring immediately after writing operation.
Abstract: Thin film perpendicular magnetic head with a narrow main pole capable of a high recording density in excess of 100 gigabits per square inch and generating a high magnetic recording field, while also being modified to suppress remanent magnetic fields occurring immediately after writing operation. A return path is provided for supplying a magnetic flux to the main pole, and an conductive coil for excitation of the main pole and return path. The main pole has a pole width of 200 nanometers or less, and a magnetic multilayer made up of a high saturation flux density layer and low saturation flux density layer. The low saturation flux density layer and the high saturation flux density suppress remanent magnetization and prevent erasing after writing by utilizing a closed magnetic domain structure in the pole.
TL;DR: In this article, Monte Carlo simulations are used to investigate the effect of surface anisotropy on the spin configurations and hysteresis loops of ferromagnetic nanoparticles.
Abstract: Monte Carlo simulations are used to investigate the effect of surface anisotropy on the spin configurations and hysteresis loops of ferromagnetic nanoparticles. Spherical particles of radius a are composed of N atoms located on a simple cubic lattice with interatomic spacing a. The particles have 213. A classical Heisenberg model is assumed, with surface and bulk anisotropy. When surface anisotropy is positive there are two types of ground states separated by a large energy barrier: a “throttled” configuration with reduced magnetization for intermediate values of surface anisotropy and a “hedgehog” configuration with zero magnetization in the strong surface anisotropy limit. Beyond a threshold, surface anisotropy of either sign induces 111 easy axes for the net magnetization. Easy-axis hysteresis loops are then square, with a continuous approach to saturation, and the effective anisotropy is deduced either from the switching field or from the initial slope of the perpendicular magnetization curve. The hedgehog state shows a stepwise magnetization curve involving discrete configurations, and it passes to a throttled configuration before saturating. The hysteresis loop has the unusual feature that it involves a state in the first quadrant, which lies on the reversible initial magnetization curve; it is possible to recover the zero-field cooled state after saturation. A survey of the exchange and anisotropy parameters for a range of ferromagnetic materials indicates that the effects of surface anisotropy on the spin configuration should be most evident in nanoparticles of ferromagnetic actinide compounds such as US, and rare-earth metals and alloys with Curie points below room temperature; the effects in nanoparticles of 3d ferromagnets and their alloys are usually insignificant, with the possible exception of FePt.
TL;DR: In this article, single-phase multiferroic BiFeO3 (BFO) ceramics were prepared by sol-gel technique after annealing in different atmospheres followed by leaching in dilute nitric acid.
TL;DR: Ferromagnetic hierarchical porous carbon (FHPC) with nickel particles embedded in the hierarchical carbon skeleton was synthesized in this article, where the hierarchical macro-mesoporous skeleton was formed by dissolving a salt template of Na2CO3.
TL;DR: In this article, the temperature dependence of magnetization, magnetic anisotropy, and coercive field of gallium-substituted cobalt ferrite was investigated for a series of compositions of CoGaxFe2−xO4.
Abstract: The temperature dependence of magnetization, magnetic anisotropy, and coercive field of gallium-substituted cobalt ferrite was investigated for a series of compositions of CoGaxFe2−xO4 (0 ⩽ x ⩽ 0.8). Hysteresis loops were measured for each sample over the range of −5 T ⩽ μ0H ⩽ 5 T for selected temperatures between 10 and 400 K. The magnetization at 5 T and low temperatures was found to increase for the lower Ga contents (x = 0.2 and 0.4) compared to pure CoFe2O4, indicating that at least initially, Ga3+ substitutes predominantly into the tetrahedral sites of the spinel structure. The high field regions of these loops were modeled using the law of approach to saturation, which represents the rotational process, together with an additional linear forced magnetization term. The first order cubic magnetocrystalline anisotropy coefficient K1 was calculated from curve fitting to these data. It was found that K1 decreased with increasing Ga content at all temperatures. Both anisotropy and coercivity increased substantially as temperature decreased. Below 150 K, for certain compositions (x = 0, 0.2, 0.4), the maximum applied field of μ0H = 5 T was less than the anisotropy field and, therefore, insufficient to saturate the magnetization. In these cases, the use of the law of approach method can lead to calculated values of K1 which are lower than the correct value.
TL;DR: In this article, a comprehensive investigation of structure, magnetism, and transport in strained epitaxial La 0.5Sr0.5CoO3 (001) films deposited on SrTiO3(001) substrates by reactive dc magnetron sputtering is presented.
Abstract: La1−xSrxCoO3 has received considerable attention in bulk form. This is due to interest in the fundamental magnetic properties (spin-state transitions and magnetic phase separation) as well as potential applications in ferroelectric memory and solid-oxide fuel cells. The structure and properties in thin film form are not well understood, and the influence of dimensional confinement on effects such as magnetic phase separation is unknown. Here, we report a comprehensive investigation of structure, magnetism, and transport in strained epitaxial La0.5Sr0.5CoO3 (001) films deposited on SrTiO3 (001) substrates by reactive dc magnetron sputtering. The crystalline quality, phase purity, strain state, oxygen stoichiometry, morphology, and magnetic and electronic properties of the epilayers are all probed and are found to be particularly sensitive to the total sputtering gas pressure and the ratio of reactive to inert gas (PO2/PAr). The various structure-property relationships are discussed in detail, particularly ...
TL;DR: In this paper, the influence of epitaxial strain on the magnetic and magnetotransport properties of LaAlO{sub 0.67}Sr{sub 1.33}MnO{Sub 3} thin films was studied.
Abstract: The influence of epitaxial strain, in the form of tetragonal distortions, on the magnetic and magnetotransport properties of La{sub 0.67}Sr{sub 0.33}MnO{sub 3} thin films was studied. The tetragonal distortion (c/a ratio) was modulated through the choice of the substrate, ranging from c/a=1.007 on (001)-oriented (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} substrates to 0.952 on (110)-oriented GdScO{sub 3} substrates. In agreement with previous theoretical predictions, these large values of tensile strain cause the Curie temperature and the saturation magnetization to decrease, alter the temperature dependence of the resistivity and magnetoresistance, and increase the resistivity several orders of magnitude.
TL;DR: A method for identifying physical parameters on the out-of-plane first-order reversal curve diagrams: the position of the irreversible part on the critical axis is a good approximation to the average value of the nanowire coercivity and the maximum interaction field is equal to the interaction field at saturation.
Abstract: First-order reversal curve diagrams have been used to investigate magnetostatic interactions and average coercivity of individual wires in soft ferromagnetic uniform length nanowire arrays. We present a method for identifying these physical parameters on the out-of-plane first-order reversal curve diagrams: the position of the irreversible part on the critical axis is a good approximation to the average value of the nanowire coercivity and the maximum interaction field is equal to the interaction field at saturation. Their dependence upon material (CoFeB and Ni) and nanowire length are presented. The magnetostatic interactions increase linearly with length, in agreement with a model developed previously. The global array coercivity, obtained from magnetization curves, is generally lower than the apparent average coercivity for individual nanowires. This coercivity reduction increases linearly with the magnetostatic interactions. The general shape of the out-of-plane first-order reversal curve diagrams is compared with those obtained from a theoretical moving Preisach model.
ENEA1
TL;DR: In this article, a nanoparticle La0.7Ca0.3MnO3 was synthesized for the first time by the glycine-nitrate method without additional heat treatment.
TL;DR: In this article, the magnetic switching of ferromagnetic nanotubes as a function of geometrical parameters has been investigated and the modes of magnetization reversal are observed to depend on the geometry of the Nanotubes.
Abstract: The magnetic switching of ferromagnetic nanotubes as function of geometrical parameters has been investigated. The modes of magnetization reversal are observed to depend on the geometry of the nanotubes. Time dependent magnetization properties reveal that the nanotubes have strong magnetic viscosity effects. The values of magnetic viscosity coefficient (S) for different applied fields are high near the coercive field.
TL;DR: This work proposes a new method of modeling SRMs based on an adaptive neural fuzzy inference system (ANFIS) that is quite accurate and in excellent agreement with experimental flux linkage measurements and the calculated torque data.
Abstract: The magnetic saturation and strong nonlinearity of switched reluctance machines (SRMs) makes it very difficult to derive a comprehensive mathematical model for the behavior of the machine. We propose a new method of modeling SRMs based on an adaptive neural fuzzy inference system (ANFIS). First, we use an indirect method to measure the static flux linkage and then use the co-energy method (via the principle of virtual displacement) to calculate the torque characteristics from data on flux linkage versus current and rotor position. A hybrid learning algorithm, which combines the back propagation algorithm and the linear least-squares estimation algorithm, identifies the parameters of the ANFIS. After training, the ANFIS flux linkage model and ANFIS torque model are in excellent agreement with experimental flux linkage measurements and the calculated torque data. Finally, we use an ANFIS current model and an ANFIS torque model to study SRM dynamic performance. The accuracy of the model was evaluated by comparison to laboratory measurements of the machine's current-speed and torque-speed characteristics. The model is quite accurate.
TL;DR: In this paper, a simple method has been developed for direct synthesis of magnetic multi-walled carbon nanotubes (MWCNTs) homogeneously decorated with size-controllable Fe nanoparticles (Fe-NPs) encapsulated by graphitic layers on the MWCNT surface by pyrolysis of ferrocene.
TL;DR: By a theoretical treatment that includes short-range repulsion in the Hofstadter treatment, stripe-like spin density-modulated phases are revealed in SrCu2(BO3)2 as emergent from a fluidic fractal spectrum.
Abstract: The fractalized Hofstadter butterfly energy spectrum predicted for magnetically confined fermions diffracted by a crystal lattice has remained beyond the reach of laboratory-accessible magnetic fields We find the geometrically frustrated spin system SrCu2(BO3)2 to provide a sterling demonstration of a system in which bosons confined by a magnetic and lattice potential mimic the behavior of fermions in the extreme quantum limit, giving rise to a sequence of plateaus at all magnetization mz/msat = 1/q ratios 9 ≥ q ≥ 2 and p/q = 2/9 (msat is the saturation magnetization) in magnetic fields up to 85 T and temperatures down to 29 mK, within the sequence of previously identified plateaus at 1/8, 1/4, and 1/3 of the saturated magnetization We identify this hierarchy of plateaus as a consequence of confined bosons in SrCu2(BO3)2 mimicking the high magnetic field fractalization predicted by the Hofstadter butterfly for fermionic systems Such an experimental realization of the Hofstadter problem for interacting fermions has not been previously achieved in real materials, given the unachievably high magnetic flux densities or large lattice periods required By a theoretical treatment that includes short-range repulsion in the Hofstadter treatment, stripe-like spin density-modulated phases are revealed in SrCu2(BO3)2 as emergent from a fluidic fractal spectrum
TL;DR: The preparation of monodisperse maghemite nanoparticle suspensions in heptane by thermal decomposition of iron(III) acetylacetonate in the presence of oleic acid and oleylamine surfactants is reported.
Abstract: We report the preparation of monodisperse maghemite (γ-Fe2O3) nanoparticle suspensions in heptane, by thermal decomposition of iron(III) acetylacetonate in the presence of oleic acid and oleylamine surfactants. By varying the surfactant/Fe precursor mole ratio during synthesis, control was exerted both over the nanocrystal core size, in the range from 3 to 6 nm, and over the magnetic properties of the resulting nanoparticle dispersions. We report field-cycling 1H NMR relaxation analysis of the superparamagnetic relaxation rate enhancement of nonaqueous suspensions for the first time. This approach permits measurement of the relaxivity and provides information on the saturation magnetization and magnetic anisotropy energy of the suspended particles. The saturation magnetization was found to be in the expected range for maghemite particles of this size. The anisotropy energy was found to increase significantly with decreasing particle size, which we attribute to increased shape anisotropy. This study can be...
TL;DR: In this article, the authors show that pressure systematically enhances the magnetic properties of titaniferous oxides (titanomagnetite), which are the principal carriers of magnetic remanence in nature.
Abstract: [1] A poorly understood facet of magnetism concerns its response to the imposition of very high pressures. Here we show that pressure systematically enhances the magnetic properties of titaniferous oxides (titanomagnetite), which are the principal carriers of magnetic remanence in nature. For example, at 4 GPa, saturation remanent magnetization intensities increase by a factor of 2, 3, 13 and 21 for titanomagnetite with 0, 20, 40 and 60% titanium in the structure, respectively. Magnetic coercivity also dramatically rises with pressure for high Ti species. The magnetization intensities and coercivities remain permanently elevated after pressure release. Pressure thus makes multidomain titanomagnetite more single domain-like, which can potentially explain deeply rooted magnetic anomalies on Earth and other planets.
TL;DR: In this paper, a combination of chemical, magnetic and optical methods was used to determine the iron speciation in atmospheric dust collected on filters at a coastal site in Gran Canaria.
TL;DR: A detailed magnetic study of urban soils in Hangzhou City, China, was carried out using combined environmental magnetism and rock magnetism techniques as discussed by the authors, which showed that those urban soils have a significant magnetic enhancement, which were characterized by higher magnetic susceptibility (average 128 × 10-8 m3·kg-1) and magnetic remanence, and low frequency-dependent susceptibility (Average 3.6%, N=182).
Abstract: A detailed magnetic study of urban soils in Hangzhou City, China, was carried out using combined environmental magnetism and rock magnetism techniques. Magnetic measurements showed that those urban soils have a significant magnetic enhancement, which were characterized by higher magnetic susceptibility (average 128 × 10–8 m3·kg–1) and magnetic remanence, and low frequency-dependent susceptibility (average 3.6%, N=182). Magnetic susceptibility values of urban soils showed highly significant negative correlation with frequency-dependent susceptibility, indicating that the mechanism of the magnetic enhancement of urban soils is different from contribution of pedogenic ferrimagnetic minerals in nature soils. Magnetic susceptibility values of urban soils, on the other hand, have significantly positive correlation with Soft IRM (IRM20mT) and saturation isotherm remanent magnetization (SIRM), suggesting that ferrimagnetic minerals are the main magnetic carriers. The combined rock magnetism (acquisition curves of IRM, temperature-dependent susceptibility and hysteresis measurement) and SEM/EDX (scanning electron microscopy and energy dispersive X-ray analysis) revealed that magnetic mineralogy of urban soils is dominated by magnetite-like and hematite-like phases. The hysteresis parameters suggested that they are present mainly in the pseudo-single domain (PSD) and multidomain (MD) grains, which is attributed to input of anthropogenic magnetic grains from industrial activity, fuel combustion and traffic pollution. This finding suggested that magnetic measurements could be used as potential tools for monitoring soil pollution, mapping spatial distribution of pollution, and differentiating source of pollutants in urban soils.
TL;DR: In this paper, strong magnetoelectric coupling was observed at microwave frequencies in metallic magnetic film/lead zirconate titanate [Pb(Zr,Ti)O3] multiferroic composites, in which the magnetic films were either FeCoB or FeGaB with relatively high saturation magnetostriction constants between 40 and 70ppm.
Abstract: Strong magnetoelectric coupling was observed at microwave frequencies in metallic magnetic film/lead zirconate titanate [Pb(Zr,Ti)O3] multiferroic composites, in which the magnetic films were either FeCoB or FeGaB with relatively high saturation magnetostriction constants between 40 and 70ppm and narrow ferromagnetic resonance linewidths of ∼20Oe at 10GHz. Large electrostatically induced ferromagnetic resonance frequency shifts of 50–110MHz at ∼2.3GHz were observed. These metallic magnetic film/Pb(Zr,Ti)O3 multiferroic composites with large electrostatic tunability of the ferromagnetic resonance frequency provide great opportunities for integrated microwave multiferroic devices.