Showing papers on "Saturation (magnetic) published in 1992"
TL;DR: A new magnetic material with appreciable optical transmission in the visible region at room temperature has been isolated as a gamma-Fe(2)O(3)/polymer nanocomposite.
Abstract: A new magnetic material with appreciable optical transmission in the visible region at room temperature has been isolated as a gamma-Fe(2)O(3)/polymer nanocomposite. The synthesis is carried out in an ion-exchange resin at 60 degrees C. Magnetization and susceptibility data demonstrate loading-dependent saturation moments as high as 46 electromagnetic units per gram and superparamagnetism for lower loadings where particle sizes are less than 100 angstroms. Optical absorption studies show that the small-particle form of gamma-Fe(2)O(3) is considerably more transparent to visible light than the single-crystal form. The difference in absorption ranges from nearly an order of magnitude in the "red" spectral region to a factor of 3 at 5400 angstroms. The magnetization of the nanocomposite is greater by more than an order of magnitude than those of the strongest room-temperature transparent magnets, FeBO(3) and FeF(3).
805 citations
TL;DR: In this paper, devitrified glassy FeCuNbSiB alloys are used to reveal a homogeneous ultrafme grain structure of bcc-FeSi with grain sizes of typically 10-15nm and random texture.
452 citations
TL;DR: In this paper, the authors reported giant magnetoresistance in [Ni81Fe19/Cu]N multilayers at 4.2 K, with an oscillation period and phase similar to that in Co/Cu multilayer.
Abstract: We report giant magnetoresistance in [Ni81Fe19/Cu]N multilayers. Saturation magnetoresistance values exceeding 16% for saturation fields of only 600 Oe are found at 300 K. In addition, we show evidence for well‐defined oscillations in saturation magnetoresistance as a function of Cu spacer layer thickness at 4.2 K, with an oscillation period and phase similar to that in Co/Cu multilayers. However, the temperature dependence of the magnetoresistance, while weak for thin Cu layers, is much stronger for thicker Cu layers. Consequently at 300 K only a single oscillation in magnetoresistance for thin Cu layers is found. We show that the properties of the Ni81Fe19/Cu multilayers are very sensitive to annealing at moderate temperatures, which may limit the possible technological applications of such structures.
197 citations
TL;DR: In this article, the phase formation and magnetic properties of Fe100−xCox powders were investigated with respect to phase formation using x-ray diffraction, differential scanning calorimetry, and measurements of the saturation magnetization and the coercivity.
Abstract: Fe100−xCox powders were prepared by mechanical alloying of the elements in a planetary ball mill They were investigated with respect to phase formation and magnetic properties using x‐ray diffraction, differential scanning calorimetry, and measurements of the saturation magnetization and the coercivity The measurement of the saturation magnetization proved the true formation of the bcc (x≤80) and fcc (x=90) solid solutions by mechanical alloying A nonequilibrium microstructure originates from a grain‐size reduction to minimum 20–30 nm and the introduction of internal strain up to 1% (root‐mean‐square strain) An improvement in the soft magnetic properties by the nanocrystalline state, as hoped for, does not occur, because the high amount of internal strain together with the high saturation magnetostriction of the Fe‐Co alloys causes relatively high coercivities of 5–40 A/cm Grain growth and strain relaxation induced by controlled heat treatment of the as‐milled powders allowed the separation of the in
176 citations
TL;DR: In this paper, the authors conducted saturation absorption experiments on the title compound at 1.064 μm with laser light propagating along both the [001] and [111] crystallographic axes.
Abstract: Saturation absorption experiments are conducted on the title compound at 1.064 μm with laser light propagating along both the [001] and [111] crystallographic axes. Rotation of the crystals about these axes during the experiments reveals that the transmission of the polarized 1.064 μm radiation is highly anisotropic in the saturation regime. The details of the anisotropy and saturation curves are explained using a simple model of subsets of optical centers along with a relevant set of rate equations. The ground and excited‐state absorption cross sections at 1.064 μm are calculated to be σgs=5.7(±2)×10−18 cm2 and σes=8(±2)×10−19 cm2, respectively, and the optimum crystallographic orientation for utilization in optical devices is discussed.
146 citations
TL;DR: In this paper, the authors demonstrate that the method of preparation of magnetites, irregularities in the crystals, and increase or decrease of the state of internal stress by quenching or annealing all have a direct effect on the amount of magnetic memory.
Abstract: Low-temperature demagnetization (LTD), consisting of zero-field cycling from room temperature to 77 K and back to room temperature, was performed on magnetites from different sources having grain sizes between 0.037 μm and 5 mm. The memory fractions, RI and RT of saturation isothermal remanent magnetization (IRMs) and 0.1 mT thermoremanent magnetization (TRM), respectively, have a strong intrinsic grain-size dependence below ≈ 10 μm, but are almost size independent in the multidomain (MD) range above 10 μm. The size dependence of RI and RT in the MD range reported by Parry [1979, 1980] probably results from stress introduced during crushing to obtain finer size fractions. We demonstrate that the method of preparation of magnetites, irregularities in the crystals, and increase or decrease of the state of internal stress by quenching or annealing all have a direct effect on the amount of magnetic memory. Magnetic memories (the fractions of TRM and IRM5 surviving after LTD) are much more resistant against alternating-field (AF) demagnetization than the original TRM and IRMs before LTD. Even large magnetite crystals (≫20 μm) reveal a hard, single-domain-like component of magnetization when the softer magnetization is removed by LTD. A comparison of AF demagnetization properties of IRMs and TRM in these MD magnetites shows that the Lowrie and Fuller [1971] test must be reinterpreted.
100 citations
04 Oct 1992
TL;DR: In this paper, a nonlinear pi-model for an induction machine operating in magnetic saturation has been developed, based on a magnetic circuit model of a rotor-stator tooth pair, with nonlinear elements representing the saturation in the rotor and in the stator.
Abstract: A novel nonlinear pi -model for an induction machine operating in magnetic saturation has been developed. It is based on a magnetic circuit model of a rotor-stator tooth pair, with nonlinear elements representing the saturation in the rotor and in the stator. The model of a tooth pair is extended to a model of the machine by assuming an infinite number of infinitesimal teeth. The model is compatible with the Blondel-Park transformation. Experimental measurements on a wound rotor machine confirm the model. Operating conditions for optimal efficiency at high torque levels requiring operation in saturation are computed with the model. >
92 citations
86 citations
TL;DR: Extraordinarily large circular dichroism has been observed in the near-edge x-ray absorption of the Fe 2p 3/2 and 2p 1/2 lines of monolayer magnetic films of Fe on Cu(001).
Abstract: Extraordinarily large circular dichroism has been observed in the near-edge x-ray absorption of the Fe 2p 3/2 and 2p 1/2 lines of monolayer magnetic films of Fe on Cu(001). This is the first reported observation of normal incidence dichroism in a metal overlayer. Analysis of such large variations using a simple and concise theoretical formulation suggests a saturation of the dichroism effect. This analytical approach also permits an approximate determination of the magnetic moment directly from experimental parameters
82 citations
TL;DR: In this paper, the axial demagnetizing field which depends on the inner core dimensions and the strength of internal and applied stresses play a decisive role in determining the switching process.
80 citations
TL;DR: In this article, the spins are found to be located on nitrogens although they are in some degree delocalized on phenyl rings, and through-bond interaction, depending on the topology of a polymer skeleton, is considered to operate between rather distant spins through the spin polarization with antiferromagnetic array of the phenyl ring.
Abstract: Ferromagnetic interaction among the spins in poly(m‐aniline) has been suggested by electron spin resonance and magnetic susceptibility measured at low temperatures. From the g‐value analysis, these spins are found to be located on nitrogens although they are in some degree delocalized on phenyl rings. Doping of this polymer with iodine leads to an increase in the spin concentration up to 1020 spins⋅(g‐polymer)−1. Saturation magnetization of 0.30 emu⋅G⋅g−1 and spin clusters of S=1 are observed in the iodine‐doped polymer from the temperature and field dependence of the magnetization. Through‐bond interaction, depending on the topology of a polymer skeleton, is considered to operate between rather distant spins through the spin polarization with antiferromagnetic array of the phenyl rings.
TL;DR: The electronic structures of hydrogen polymolecules in a superstrong magnetic field typically found on the surface of a neutron star are studied, and the structure of negative H ions in a high magnetic field is considered.
Abstract: The electronic structures of hydrogen polymolecules H(n) (n = 2,3,4,...) is studied in a superstrong magnetic field (B greater than about 10 exp 12 G) typically found on the surface of a neutron star. Simple analytical scaling relations for several limiting cases (e.g., large n, high B field) are derived. The binding energies of H(n) molecules are numerically calculated for various magnetic-field strengths. For a given magnetic-field strength, the binding energy per atom in the H(n) molecules is found to approach a constant value as n increases. For typical field strengths of interest, energy saturation is essentially achieved once n exceeds 3 to 4. Also considered is the structure of negative H ions in a high magnetic field. For B about 10 exp 12 G, the dissociation energy of an atom in a hydrogen chain and the ionization potential of H(-) are smaller than the ionization potential of neutral atomic hydrogen.
TL;DR: In this article, the transient behavior of the longitudinal magnetization of the mobile protons in aqueous heterogeneous materials is investigated both theoretically and experimentally when selective saturation is applied by off-resonance, RF irradiation to the homogeneously broadened, immobile protons which are coupled to the mobile particles through cross relaxation.
TL;DR: In this article, a hexagonal plate-like Co-Ti and Co-Sn substituted barium ferrite particles were prepared by a method which combines the chemical coprecipitation process and the salt flux process.
TL;DR: A high‐power pulse spectrometer was used to investigate the dynamics of magnetization transfer in cartilage in vitro, and the use of pulsed methods to generate magnetization contrast may in some circumstances offer advantages over the steady‐state saturation methods used hitherto.
Abstract: Saturating irradiation far off-resonance can lead to diminution in the water signal seen in MRI, giving rise to magnetization transfer contrast. This results from transfer of magnetization between "solid" protons with restricted motion, which give rise to a band some tens of kilohertz wide, and the narrow signal from mobile protons. In the work reported here a high-power pulse spectrometer, which can detect signals from both mobile and immobile protons, was used to investigate the dynamics of magnetization transfer in cartilage in vitro. Magnetization transfer in modified Hoffman-Forsen inversion transfer experiments was well-described by a single rate constant model; full analytical solutions are offered for the resultant biexponential magnetization recovery curves. The use of pulsed methods to generate magnetization contrast may in some circumstances offer advantages over the steady-state saturation methods used hitherto.
Book•
23 Jun 1992
TL;DR: In this paper, the authors describe the properties of superconducting materials and their applications in computer simulation, including magnetic energy storage, magnetoelastic effects, and flux creep phenomena.
Abstract: Selected articles. AC applications of superconducting materials. AC losses in superconducting materials. Amorphous superconductors. Anisotropy in magnetic materials. Anisotropy in superconducting materials. Biomagnetic measurements. Chevrel phases. Coercivity and domain wall pinning. Coherence length, proximity effect and fluctuations. Design with magnetic materials. Design with magnetic materials: computer simulation. Domains and domain walls. Ferrites, hard. Fluids, magnetic. Flux creep phenomena. Flux pinning and the summation of pinning forces. Granular superconductors. High-frequency impedance of superconducting materials. High-frequency properties of magnetic materials. Josephson effects in weak links. Magnetic energy storage. Magnetic properties of superconductors. Magnetic separation. Magnetic storage media. Magnetic units and material specification. Magnetization imaging. Magnetocaloric effect. Magnetoelastic phenomena. Magnetooptic materials. Magnetooptic storage media. Millimeter-wave detection. Multifilamentary superconducting composites. Nanocrystalline soft magnetic materials. Niobium-titanium alloys. Nonequilibrium superconductivity. Nuclear magnetic resonance imaging. Optical properties of superconductors. Organic and molecular ferromagnets. Oxide glasses as magnetic materials. Oxide superconductors: ceramic processing. Oxide superconductors: physical properties. Oxide superconductors: thin-film deposition. Power loss in magnetic materials. Radiation effects on magnetic materials. Radiation effects on superconducting materials. Superconducting magnets. Superconducting materials: BCS and phenomenological theories. Thin films and multilayers, magnetic.
Patent•
04 Mar 1992TL;DR: A magnetic thin-film memory as mentioned in this paper is a memory device having information recorded in a magnetic thin film thereof by the direction of magnetization, and adapted to reproduce the recorded information on the basis of the voltage generated as a result of the change of the magnetization direction due to the extraordinary Hall effect, magnetoresistance effect or the like.
Abstract: A magnetic thin film memory device having information recorded in a magnetic thin film thereof by the direction of magnetization, and adapted to reproduce the recorded information on the basis of the voltage generated as a result of the change of the magnetization direction due to the extraordinary Hall effect, magnetoresistance effect or the like. A magnetic thin film memory device in which a magnetic thin film is formed of ferrimagnetic substance having perpendicular magnetic anisotropy, and producing extraordinary Hall effect in the composition of RE rich and having the minimum saturation field which enables recording in a small magnetic field and is hard to be influenced by temperatures.
TL;DR: In this paper, Co/Cu multilayers have been grown in ultrahigh vacuum on Au(111) buffer layers and their structure is fcc (111) with atomically flat interfaces.
TL;DR: A combined magnetic vector potential, magnetic scalar potential method of computation of 3D magnetic fields by finite elements, in combination with state modeling in the abc frame of reference, is used for global 3-D magnetic field analysis and machine performance computation under rated load and overload condition in an example 14.3 kVA modified Lundell alternator as discussed by the authors.
Abstract: A combined magnetic vector potential, magnetic scalar potential method of computation of 3-D magnetic fields by finite elements, in combination with state modeling in the abc frame of reference, is used for global 3-D magnetic field analysis and machine performance computation under rated load and overload condition in an example 14.3 kVA modified Lundell alternator. The results vividly demonstrate the 3-D nature of the magnetic field in such machines and show how this model can be used as an excellent tool for computation of flux density distributions, armature current and voltage waveform profiles, and harmonic contents, as well as for computation of torque profiles and ripples. Use of the model in gaining insight into locations of regions in the magnetic circuit with heavy degrees of saturation is demonstrated. Experimental results which correlate well with the simulations of the load case are given. >
01 Jan 1992
TL;DR: In this paper, the magnetic free energy of a ferromagnetic crystal is composed of the energy of magnetic anisotropy, which is the energy connected with magnetostriction deformation of the body.
Abstract: Publisher Summary A ferromagnetic crystal in the non-magnetized state consists of separate regions of spontaneous magnetization, each of which is magnetized to saturation. The magnetic free energy of a ferromagnetic crystal is composed of the energy of magnetic anisotropy. The energy connected with magnetostriction deformation of the body should also be taken into account in cubic crystals. It should be determined from the minimum condition of the total energy for a given orientation of the layers, after which the most advantageous orientation of the layers themselves with respect to the coordinate planes has to be determined from the same condition. The width of the layers, however, is found to be inexpressible explicitly in the general case. In regard to the experimental data on the ferromagnetic structure of iron, quite a large number of investigations are available in which this structure was studied by the well-known method of ferromagnetic powders or colloids.
01 Jan 1992
TL;DR: In this article, the authors stabilize the PrMo1.5Fe10.5 compounds and their nitrides with ThMn12-type structure by using x-ray diffraction technique and thermomagnetic measurements.
Abstract: We succeed in stabilizing the PrMo1.5Fe10.5 compounds and their nitrides with ThMn12‐type structure. The single phase was identified by using x‐ray diffraction technique and thermomagnetic measurements. In PrMo1.5Fe10.5Nx, the c‐axis is the easy magnetization direction from 0 K to Curie temperature. The anisotropy field is up to 147 KOe at 1.5 K and 110 KOe at room temperature. In combination with a high Curie temperature of 640 K and a large saturation magnetization of 141.70 emu/g, these intrinsic magnetic properties are favorable for permanent magnet applications. As a preliminary attempt, a coercive force of 3.0 and 10.0 KOe was obtained at 300 and 1.5 K, respectively, by using hydrogenation disproportionation and desorption (HDD) processing.
TL;DR: The saturation transfer electron spin resonance (STESR) spectra of 10 different positional isomers of phosphatidylcholine spin-labeled in the sn-2 chain led to an increase in the diagnostic STESR line height ratios in all regions of the spectrum, reflecting the decrease in chain mobility accompanying formation of the subgel phase.
TL;DR: In this paper, the hyperline parameters of relatively well crystallized grelgite (Fe3S4) have been determined by Mossbauer spectroscopy on a natural greigite-smythite sample.
Abstract: The hyperline parameters of relatively well crystallized grelgite (Fe3S4) have been determined by Mossbauer spectroscopy on a natural greigite-smythite sample. Applied-field measurements confirm the ferrimagnetic behavior. Saturation values of the magnetic hyperfine fields are 31.8 and 33.0 T for the tetrahedral and octahedral Fe respectively. The temperature dependence implies a Curle temperature of at least 800K. In addition, the analyses of the spectra provide some information about smythite for which the spectra seem to be composed of at least three sextets.
TL;DR: In this article, a combination of a high saturation magnetization and a high magnetic permeability in the MHz range is required for video record/play-back heads used in video recorders.
Abstract: Soft magnetic multilayers are new materials that have been developed for record/play-back heads used in video recorders. For this application a combination of a high saturation magnetization and a high magnetic permeability in the MHz range is required. This has been realized in multilayer materials by making the crystallites of the material smaller than the width of the transition regions between the magnetic domains they contain.
TL;DR: In this paper, the X-ray diffraction patterns and the thermomagnetic curves of Dy2Fe17Cx with x = 1.5, 2.5 and 3.0 have been successfully prepared by the melt-spinning method.
Abstract: The carbides Dy2Fe17Cx with x=1.5-3.0 have been successfully prepared by the melt-spinning method. The X-ray diffraction patterns and the thermomagnetic curves show that they are of single phase in general with Th2Zn17 structure type when x=1.5, 2.0, 2.5 and 2.8 with a small amount of alpha -Fe as an impurity phase, while for x=3.0 the proportion of the alpha -Fe phase is high. The lattice parameters a and c are both enlarged and increase with the carbon content x. The Curie temperatures Tc are greatly enhanced when x<2.5 and remain almost constant when x=2.5-3.0, but the saturation magnetizations, sigma s, increase slightly. The Dy2Fe17Cx ribbons still maintain the rhombohedral Th2Zn17-type structure after being annealed at 1100 degrees C for 14 h, which indicates the high stability of Dy2Fe17Cx (x=1.5-3.0) compounds obtained by rapid solidification. The heat-treated ribbon samples can be magnetically oriented and prefer an easy-plane anisotropy at room temperature.
TL;DR: In this paper, a moving Preisach-type model with reversible magnetization is introduced to calculate the height of minor loops originating from negative saturation in a particulate recording media.
Abstract: Full characterization of particulate recording media requires the modeling of both the reversible and the irreversible components of the magnetization. Experiments show that the height of minor loops originating from negative saturation is not an even function of the magnetization. A moving Preisach-type model with reversible magnetization that is capable of calculating these results is introduced. The properties of the model are discussed. It is shown that previous models are special cases of this model. >
Patent•
04 Mar 1992
TL;DR: Uniaxially oriented soft magnetic thin film consists essentially of 1 to 15 atomic percent of Co and/or Ni, and the balance being Fe, and has a crystal structure of a body-centered cubic system, wherein the film is oriented substantially in the [111] direction and the absolute value of the saturation magnetostriction λ f of the film was not more than 5×10 -6.
Abstract: Uniaxially oriented soft magnetic thin film consists essentially of 1 to 15 atomic percent of Co and/or Ni, and the balance being Fe, and has a crystal structure of a body-centered cubic system, wherein the film is oriented substantially in the [111] direction and the absolute value of the saturation magnetostriction λ f of the film is not more than 5×10 -6 . The film has low coercivity 1 Oe or less and high magnetic permeability maintaining high saturation magnetic flux density of 18 kG or more. λ f reaches zero and is adjustable. Addition of 0.2 to 20 atomic percent of Ru, Mn, Cr and/or V increases wear resistance. The film is formed by deposition on {111} plane of GaAs substrate, or on c-plane of hexagonal B 8 stracture.
TL;DR: In this paper, a Co-Fe amorphous wire after annealing under tensile stress was shown to exhibit a similar behavior to that reported in metallic glass ribbons with similar composition.
TL;DR: In this article, the authors investigated the metamagnetic transition from antiferromagnetic spin structure to ferromagnetic one for an easy axis external field for Co-Fe/Cu multilayers with giant magnetoresistance, which were prepared on MgO(110) substrates using ion beam sputtering.
Abstract: Magnetization processes are investigated by calculation and experiments for Co‐Fe/Cu multilayers with giant magnetoresistance, which are prepared on MgO(110) substrates using ion beam sputtering and have in‐plane uniaxial magnetic anisotropy (Ku). The experiments show the metamagnetic transition from antiferromagnetic spin structure to ferromagnetic one for an easy axis external field. This is supported by calculation of the magnetic phase diagram for stable magnetization configurations, which shows the metamagnetic transition to occur for (J12/d)/Ku≤1, where J12 is antiferromagnetic layer interaction and d is magnetic layer thickness. The saturation fields from antiferromagnetic to ferromagnetic spin structures are substantially decreased by induction of the in‐plane uniaxial anisotropy. The relation Hsh − 2Hse = 2Ku/Ms, found for the saturation fields by the calculation, is confirmed experimentally for the multilayers, where Ms is the saturation magnetization, and Hse and Hsh are the saturation fields f...