Showing papers on "Saturation (magnetic) published in 2006"
TL;DR: In this article, the magnetic and electrical properties on magnetic Heusler alloy Ni50Mn36Sn14 were studied in magnetic fields up to 18T in 4.2-270k temperature range.
Abstract: The magnetic and electrical properties on magnetic Heusler alloy Ni50Mn36Sn14 were studied in magnetic fields up to 18T in 4.2–270K temperature range. It was found that at the vicinity of 160K the resistivity jump of 46% is accompanied by the magnetic phase transition. Furthermore, the large magnetoresistance effect of 50% by the magnetic field induced magnetic phase transition was observed.
248 citations
TL;DR: In this paper, mixed manganese-zinc and nickel zinc ferrites of composition Mn0.2Ni0.8−xZnxFe2O4 where x = 0.4, 0.5 and 0.6 were synthesized by the citrate precursor technique.
179 citations
TL;DR: In this article, the temperature variation of magnetic anisotropy and coercive field of magnetoelastic manganese-substituted cobalt ferrites (CoMnxFe2?xO4 with 0? x? 0.6) was investigated.
Abstract: The temperature variation of magnetic anisotropy and coercive field of magnetoelastic manganese-substituted cobalt ferrites (CoMnxFe2?xO4 with 0 ? x ? 0.6) was investigated. Major magnetic hysteresis loops were measured for each sample at temperatures over the range 10–400 K, using a superconducting quantum interference device magnetometer. The high-field regimes of the hysteresis loops were modeled using the law of approach to saturation equation, based on the assumption that at sufficiently high field only rotational processes remain, with an additional forced magnetization term that was linear with applied field. The cubic anisotropy constant K1 was calculated from the fitting of the data to the theoretical equation. It was found that anisotropy increases substantially with decreasing temperature from 400 to 150 K, and decreases with increasing Mn content. Below 150 K, it appears that even under a maximum applied field of 5 T, the anisotropy of CoFe2O4 and CoMn0.2Fe1.8O4 is so high as to prevent complete approach to saturation, thereby making the use of the law of approach questionable in these cases.
158 citations
TL;DR: In this paper, a modified flame synthesis method was used to produce air stable cobalt nanoparticles with a production rate of 30 g h−1 by highly reducing conditions under varying fuel to oxygen ratio.
Abstract: Air stable cobalt nanoparticles have been prepared continuously at a production rate of 30 g h−1 by a modified flame synthesis method under highly reducing conditions. Nanoparticles of 20–60 nm in diameter consisted of metallic face-centered-cubic cobalt. The metal particles were protected against oxidation by a surface layer of less than 1 nm of cobalt oxide. The material was highly magnetic exhibiting a high saturation magnetisation (>124 emu g−1) together with a low (<100 Oe) coercivity. Experiments under varying fuel to oxygen ratio were combined with thermodynamic calculations to illustrate the necessity for highly reducing conditions and enhanced gas mixing to enable the formation of metallic cobalt nanoparticles in flames.
150 citations
TL;DR: In this article, the perovskite single phase of the BiFeO3 thin film was analyzed, and the crystal structure showed the tetragonal structure with a space group P4mm.
Abstract: Ferroelectric BiFeO3 thin films were grown on Pt∕TiO2∕SiO2∕Si substrates by pulsed-laser deposition. From the x-ray diffraction analysis, the BiFeO3 thin films consist of perovskite single phase, and the crystal structure shows the tetragonal structure with a space group P4mm. The BiFeO3 thin films show enhanced electrical properties with low leakage current density value of ∼10−4A∕cm2 at a maximum applied voltage of 31V. This enhanced electrical resistivity allowed the authors to obtain giant ferroelectric polarization values such as saturation polarizations of 110 and 166μC∕cm2 at room temperature and 80K, respectively.
148 citations
TL;DR: In this paper, ZnO single crystals have been implanted with Gd ions at 180keV ion energy and two different fluences and it was found that for a fluence of 5×1015Gd+∕cm2, postimplantation annealing leads to an increase of the saturation moment up to 1.8μB∕Gd at 300K.
Abstract: In order to introduce ferromagnetic properties, ZnO single crystals have been implanted with Gd ions at 180keV ion energy and two different fluences. Magnetization reversal hysteresis loops have been recorded for as-implanted as well as annealed samples using a superconducting quantum interference device. It was found that for a fluence of 5×1015Gd+∕cm2, postimplantation annealing leads to an increase of the saturation moment up to 1.8μB∕Gd at 300K. Structural investigations revealed no secondary phase formation.
102 citations
TL;DR: The structural and magnetic properties of MnFe1-xCoxGe compounds with x=0,0.1, 0.3, 0,4, 0.,5,0,6,0.,7,0 and 1.0 were investigated by means of X-ray diffraction (XRD) and magnetization measurements.
Abstract: The structural and magnetic properties of MnFe1-xCoxGe compounds with x=0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.85,0.9, and 1.0 were investigated by means of X-ray diffraction (XRD) and magnetization measurements. XRD shows that the MnFe1-xCoxGe compounds crystallize in the hexagonal Ni2In-type crystal structure for xles0.8 and in the orthorhombic NiTiSi-type structure for x>0.8. The magnetization measurements show that the MnFe1-xCoxGe compounds exhibit a complex magnetic behavior. The Curie temperature increases with increasing of x. The saturation magnetization of the compounds with Ni2In type structure increase with increasing of x and the saturation of the magnetization in the NiTiSi-type structure also increases with increasing x. We investigated the magnetocaloric effects in these compounds by means of magnetization measurements. The maximum magnetic-entropy change observed in these compounds reaches 9 J/kgK for x=0.8 in a field change from 0 to 5 T at around 289 K
100 citations
TL;DR: In this paper, the authors report the discovery of excellent soft-ferromagnetic BGAs in FeMoPCBSi system, without the expensive element Ga, which can be cast into glassy alloy rods with diameters range up to 4mm by copper mold casting.
Abstract: The development of Fe-based bulk glassy alloys (BGAs) with high glass-forming ability has become a very hot research topic, not only because of the soft-magnetic properties, but also of the high fracture strength. Here we report the discovery of excellent soft-ferromagnetic BGAs in FeMoPCBSi system, without the expensive element Ga, which can be cast into glassy alloy rods with diameters range up to 4mm by copper mold casting. These low cost Fe-based ferromagnetic BGAs exhibit high saturation magnetization of 1.27–1.44T and superhigh initial permeability of 13 400–25 000 at 1kHz under a field of 1A∕m.
99 citations
TL;DR: In this article, the authors tried to suppress the crystalline phase by changing the Ar partial pressure (PAr) during deposition and found that the optimal condition is PAr=5×10−3Torr.
Abstract: CoFeB films were deposited on glass substrate by the sputtering method. From x-ray-diffraction and electron-diffraction-ring patterns, the major phase in the as-deposited CoFeB film is amorphous (or nanocrystalline). However, we could also identify a minor CoFe(110) crystalline phase in the film. We have tried to suppress this crystalline phase by changing the Ar partial pressure (PAr) during deposition and found that the optimal condition is PAr=5×10−3Torr. Because the electrical resistivity value (ρ) of the film is in general larger than 100μΩcm, it also indicates that the amorphous phase is dominant. From the temperature coefficient of resistance measurement, we learn that the amorphous phase in the CoFeB film crystallizes in succession at two higher temperatures (Tcr1 and Tcr2) than the room temperature (RT). Besides the electrical properties, the film thickness (tf) dependence of saturation magnetization (Ms), saturation magnetostriction (λs), and coercivity (Hc) has also been discussed. From the Aug...
98 citations
TL;DR: In this paper, a new chemical composition was identified that achieves a saturation induction of 1.64 T in an iron-based amorphous alloy, when used in electrical transformers.
97 citations
TL;DR: In this paper, the authors investigated the magnetization process of the melt-spun (Fe0.75B0.15Si0.10) 100−xNbx (x=1-4) glassy alloys to clarify the origin of low coercivity.
Abstract: The density and the magnetization process of the melt-spun (Fe0.75B0.15Si0.10)100−xNbx (x=1–4) glassy alloys have been investigated to clarify the origin of low coercivity (Hc). Both Hc and the difference of the densities between the crystalline and glassy phases, which corresponds to the free volume in the glassy phase, decrease with increasing Nb content. An analysis of the magnetization process based on the law of approach to ferromagnetic saturation reveals that quasidislocation dipole (QDD)-type defects are the main sources of elastic stress. The results also suggest that the pinning force for magnetic domain walls generated by one QDD-type defect is independent of the Nb content, but the number density of QDDs decreases with increasing the Nb content. Therefore, it concluded that the origin of low Hc of the glassy alloys is the low number density of QDDs which corresponds to the low number density of the domain-wall pinning sites.
TL;DR: In this article, the micromagnetic behavior near edges of ferromagnetic thin films when uniform fields are applied in plane and perpendicular to the edge was modeled and a simple macrospin model for the edge magnetization was developed.
Abstract: This paper describes modeling of the micromagnetic behavior near edges of ferromagnetic thin films when uniform fields are applied in plane and perpendicular to the edge. For ideal film edges with vertical edge surfaces, the field required to saturate the magnetization perpendicular to the edge, ${H}_{\mathrm{sat}}$, and the frequency of precession in the localized edge mode are calculated using numerical micromagnetics for a wide range of film thicknesses. Analysis of the critical state at the saturation field and the full micromagnetic results are used to develop a simple macrospin model for the edge magnetization. This model predicts both ${H}_{\mathrm{sat}}$ and edge mode precession frequency values that agree well with the micromagnetic results. Three classes of nonideal edges are also modeled: tilted edge surfaces, diluted magnetization near the edge, and surface anisotropy on the edge surface. Despite their different physical mechanisms, all three of these defects produce similar reductions in ${H}_{\mathrm{sat}}$ and similar dynamic properties of the edge magnetization.
TL;DR: Results showed that the obtained Zn-Mn ferrites had spinel structure and high purity at the calcining temperatures of 850-1250 degrees C, and with the increase of calcining temperature, the finer crystalline structure could be formed, and their intensity of saturation magnetization reached the highest value at 11 50 degrees C.
TL;DR: In this paper, the photoluminescence (PL) in the red (622nm) of GaN films was investigated and the maximum PL intensity was obtained at a Ga flux of 3.6×10−7Torr.
Abstract: GaN films were doped with Eu to a concentration of ∼0.12at.% during growth at 800°C by molecular beam epitaxy, with the Eu cell temperature held constant at 470°C. All samples were postannealed at 675°C. The films exhibited strong photoluminescence (PL) in the red (622nm) whose absolute intensity was a function of the Ga flux during growth, which ranged from 3.0×10−7to5.4×10−7Torr. The maximum PL intensity was obtained at a Ga flux of 3.6×10−7Torr. The samples showed room temperature ferromagnetism with saturation magnetization of ∼0.1–0.45emu∕cm3, consistent with past reports where the Eu was found to be predominantly occupying substitutional Ga sites. There was an inverse correlation between the PL intensity and the saturation magnetization in the films. X-ray diffraction showed the presence of EuGa phases under all the growth conditions but these cannot account for the observed magnetic properties.
Patent•
28 Nov 2006TL;DR: In this paper, a highly accurate optical pumping magnetometer is presented, in which a static magnetic field and an oscillating field to be applied to a vapor cell are stabilized, and the magnetometer drive circuits for driving the fluxgate magnetometers, current converters for converting outputs of the magnetometers drive circuits into amount of currents, and magnetic field generating coils for generating a magnetic field in a phase opposite to the environmental magnetic noise in two directions.
Abstract: Provided is a highly accurate optical pumping magnetometer, in which a static magnetic field and an oscillating field to be applied to a vapor cell are stabilized. To this end, the optical pumping magnetometer includes: Helmholtz coils for applying a constant static magnetic field to a vapor cell serving as a magnetic field detector; fluxgate magnetometers for detecting environmental magnetic noise in two directions of X-axis direction and Y-axis direction other than Z-axis direction which is a direction for detecting a magnetic field coming out of a measurement object while locating the vapor cell in the center thereof; magnetometer drive circuits for driving the fluxgate magneotometers; current converters for converting outputs of the magnetometer drive circuits into amount of currents; and magnetic field generating coils for generating a magnetic field in a phase opposite to the environmental magnetic noise in the two directions.
TL;DR: The first successful synthesis of the CoFe−B−Si-based bulk glassy alloys exhibiting superhigh fracture strength and excellent soft-magnetic properties with extremely low magnetostriction is encouraging for future development of Co-based Bulk Glassy Alloys as new engineering and functional materials as discussed by the authors.
Abstract: Co-based bulk glassy alloys with diameters up to 4mm were formed in a [(Co1−xFex)0.75B0.2Si0.05]96Nb4 system. The bulk glassy alloys exhibit a superhigh fracture strength of 3980–4170MPa and Young’s modulus of 190–210GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.71–0.97T, low coercive force of 0.7–1.8A∕m, high permeability of 1.48–3.25×104, and extremely low saturation magnetostriction of 0.55–5.76×10−6. The first successful synthesis of the Co–Fe–B–Si-based bulk glassy alloys exhibiting superhigh fracture strength and excellent soft-magnetic properties with extremely low magnetostriction is encouraging for future development of Co-based bulk glassy alloys as new engineering and functional materials.
TL;DR: In this paper, YIG powders with particle sizes of 9, 14, 25 and 60 nm have been synthesized and their magnetic properties have been studied as a function of particle size and temperature.
01 Dec 2006
TL;DR: In this article, an amorphous CoZrTa alloy exhibiting high permeability, good high-temperature stability (>250degC), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss was used in combination with magnetic vias and elongated structures that take advantage of the uniaxial magnetic anisotropy.
Abstract: On-chip inductors with 2 levels of magnetic material were integrated into an advanced 130 nm CMOS process to obtain over an order of magnitude (>14times) increase in inductance and Q-factor, significantly greater than prior values of 2.3times for high frequency inductors. The magnetic material is shown to operate at frequencies beyond 6.4 GHz for 1 nH inductors. An amorphous CoZrTa alloy exhibiting high permeability, good high-temperature stability (>250degC), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatible with silicon technology was used in combination with magnetic vias and elongated structures that take advantage of the uniaxial magnetic anisotropy
TL;DR: In this paper, the growth of aligned filled carbon nanotubes on iron and cobalt pre-coated Si-substrates and their dependence on the deposition time were studied.
TL;DR: In this article, the authors have grown LaMnO3 thin films on (001) LaAlO3 substrates by pulsed laser deposition X-ray diffraction confirms that the films are only slightly relaxed and are oriented "square on square" relative to the substrate.
Abstract: We have grown LaMnO3 thin films on (001) LaAlO3 substrates by pulsed laser deposition X-ray diffraction confirms that the films are only slightly relaxed and are oriented “square on square” relative to the substrate The measured Raman spectra closely resemble that observed in bulk LaMnO3, which indicates no relevant distortions of the MnO6 octahedra induced by the epitaxial strain Therefore, no detectable changes in the lattice dynamics occurred in our LaMnO3 strained films relative to the bulk case Mn55 nuclear magnetic resonance identifies the presence of localized Mn4+ states Superconducting quantum interference device magnetization measures TN=131(3)K and a saturation moment μ=109μB∕Mn, revealing a small concentration of Mn4+ and placing our films within the antiferromagnetic insulating phase
TL;DR: In this article, a core-shell structure of a TiO2/BaFe12O19 composite nanoparticles that can photodegrade organic pollutants in the dispersion system effectively and can be recycled easily by a magnetic field is reported.
TL;DR: In this article, the effect of magnetic field on the intensity of electroluminescence from devices made of a poly-$p$-phenylenevinylene (PPV) copolymer was investigated.
Abstract: The effect of magnetic field on the intensity of electroluminescence from devices made of a poly-$p$-phenylenevinylene (PPV) copolymer was investigated. The emission intensity was enhanced by the application of magnetic field, and the magnitude of the increase depended on operational voltages. When the device was operated under application of low voltages, the intensity increased with magnetic field and reached an 8.5% increase at about $100\phantom{\rule{0.3em}{0ex}}\mathrm{mT}$. With the increase of the operational voltage, the effect of magnetic field was lessened. In addition, when measured at high voltages with increasing magnetic field, the emission intensity started to decrease after passing a maximum, then leveled off. This saturation value was slightly higher than that observed in the absence of magnetic field. These findings suggest that two processes sensitive to magnetic field are included in the emission processes. They are assigned to the charge recombination (CR) of anion and cation radicals and triplet-triplet annihilation (TTA) processes. From the analysis of the effects of magnetic field on the emission intensity based on a kinetic model, we quantitatively determined the fractions of singlet and triplet excitons generated through the CR process to be 0.17 and 0.83, respectively. With the increase of the concentration of triplet excitons in the organic layer, production of singlet excitons through the TTA process was enhanced, and the total yield of the singlet excitons exceeded 0.5 under normal device operational conditions. We conclude that this high yield is responsible for the high emission efficiency observed in the light-emitting devices based on PPVs.
TL;DR: In this paper, a core-shell structure of strontium ferrite nanoparticles was obtained by using a citrate precursor technique with a Fe/Sr ratio of 10.8.
TL;DR: In this article, a magnetic gas sensing methodology was proposed to detect hydrogen using the ferromagnetic properties of a nanoscale dilute magnetic semiconductor Sn0.95Fe0.05O2.
Abstract: The authors report on a magnetic gas sensing methodology to detect hydrogen using the ferromagnetic properties of a nanoscale dilute magnetic semiconductor Sn0.95Fe0.05O2. This work demonstrates the systematic variation of saturation magnetization, coercivity, and remanence of Sn0.95Fe0.05O2 with the hydrogen gas flow rate, thus providing clear experimental evidence of the concept of magnetic gas sensing (using the magnetic property of a material as a gas sensing parameter). Based on the results of using hydrogen as an example for reducing gases, it is believed that any reducing gas capable of changing the oxygen stoichiometry of Sn0.95Fe0.05O2 can be detected using this method. Furthermore, this method presents an alternative gas sensing technology without the use of the electrical contacts.
TL;DR: In this paper, a two-dimensional two-component random conductor mixture is described as a superconducting wire network, which can survive in a broad field range in the BaFe12O19 hybrid.
Abstract: Inhomogeneous magnetic fields generated by the BaFe12O19 ferromagnetic substrate create a magnetic template for superconducting condensate in the Nb/BaFe12O19 hybrids. Depending on the field and temperature, the magnetic template guides superconductivity to nucleate in different areas: above the magnetic domain walls of the BaFe12O19 forming the domain-wall superconductivity DWS , above the reversed magnetic domains RDS , and above the positive magnetic domains forming bulk superconductivity. The DWS, behaving as a superconducting wire network, survives in a broad field range. The RDS, existing in the form of isolated superconducting islands near the saturation field Hs of BaFe12O19, can be described as a twodimensional two-component random conductor mixture. Being related to the hysteretic domain evolution, superconducting condensate above the reversed domains shows pronounced switching behavior.
TL;DR: In this paper, the authors demonstrate the importance of magnetostatic interactions in dense arrays of ferromagnetic nanowires and show that the high field behavior of such arrays is dominated by magnetostastic effects and that a nanowire array behaves like a double-sided distribution of magnetic monopoles.
TL;DR: In this paper, the authors derived the uniaxial anisotropy, cubic anisotropic, saturation magnetic induction, and saturation magnetostriction values from measurements of the magnetization and magnetstriction of stress-annealed Galfenol (Fe100-xGax,x=12.5,18.4, and 22.0) and Fe81Al19 as a function of compressive stresses <100 MPa.
Abstract: Values of the uniaxial anisotropy, cubic anisotropy, saturation magnetic induction, and saturation magnetostriction were obtained from measurements of the magnetization and magnetostriction of stress-annealed Galfenol (Fe100-xGax,x=12.5,18.4, and 22.0)and Fe81Al19 as a function of compressive stresses <100 MPa. The values were derived from fitting magnetization and magnetostriction curves to the energy expression Ei=-mu 0MsHalphaz+Kcubic(alpha x 4+alphay 4+alphaz 4)+Ku niaxialalphaz 2-lambdasatTalphaz 2, where Ms,lambdasat and the K's are fit parameters. The alphai's are the direction cosines of the magnetization direction with respect to the field and stress direction (z).H is the magnetic field and T is the measurement stress (compressive T<0). Data are fit with high precision by only the above four constants plus a smoothing constant. Importantly, Kuniaxial enables a prediction of the maximum usable tensile stress
TL;DR: In this paper, the magnetic susceptibility of the magnetic fluid with CoFe 2 O 4 particles was measured in the low-frequency range in order to determine mean values of magnetic grain size and the saturation magnetisation.
TL;DR: In this paper, an extensive experimental study of the Gilbert damping parameter of multicomponent metal oxides micro-and nanophases was conducted to determine changes in the microwave absorption over the 6-18\phantom{\rule{0.3em}{0ex}}\mathrm{GHz} frequency range as a function of composition and static magnetic field.
Abstract: The microwave damping mechanisms in magnetic inhomogeneous systems have displayed a richness of phenomenology that has attracted widespread interest over the years. Motivated by recent experiments, we report an extensive experimental study of the Gilbert damping parameter of multicomponent metal oxides micro- and nanophases. We label the former by $M$ samples, and the latter by $N$ samples. The main thrust of this examination is the magnetization dynamics in systems composed of mixtures of magnetic $(\ensuremath{\gamma}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3})$ and nonmagnetic (ZnO and epoxy resin) materials fabricated via powder processing. Detailed ferromagnetic resonance (FMR) measurements on $N$ and $M$ samples are described so to determine changes in the microwave absorption over the $6--18\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$ frequency range as a function of composition and static magnetic field. The FMR linewidth and the field dependent resonance were measured for the $M$ and $N$ samples, at a given volume fraction of the magnetic phase. The asymmetry in the form and change in the linewidth for the $M$ samples are caused by the orientation distribution of the local anisotropy fields, whereas the results for the $N$ samples suggest that the linewidth is very sensitive to details of the spatial magnetic inhomogeneities. For $N$ samples, the peak-to-peak linewidth increases continuously with the volume content of magnetic material. The influence of the volume fraction of the magnetic phase on the static internal field was also investigated. Furthermore, important insights are gleaned through analysis of the interrelationship between effective permeability and Gilbert damping constant. Different mechanisms have been considered to explain the FMR linewidth: the intrinsic Gilbert damping, the broadening induced by the magnetic inhomogeneities, and the extrinsic magnetic relaxation. We observed that the effective Gilbert damping constant of the series of $N$ samples are found to be substantially smaller in comparison to $M$ samples. This effect is attributed to the surface anisotropy contribution to the anisotropy of ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ nanoparticles. From these measurements, the characteristic intrinsic damping dependent on the selected material and the damping due to surface/interface effects and interparticle interaction were estimated. The inhomogeneous linewidth (damping) due to surface/interface effects decreases with diminishing particle size, whereas the homogeneous linewidth (damping) due to interactions increases with increasing volume fraction of magnetic particles (i.e., reducing the separation between neighboring magnetic phases) in the composite.
TL;DR: In this paper, the edge-mode frequency goes to zero at the edge saturation field and becomes much less distinct for applied fields misaligned from the edge normal by as little as 1°.
Abstract: We have used “trapped spin wave” or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field relationship depends on whether the edge surface is vertical or tapered, while the “bulk” modes are nearly unaffected. The models show the edge-mode frequency going to zero at the edge saturation field. This critical field becomes much less distinct for applied fields misaligned from the edge normal by as little as 1°. Ferromagnetic-resonance and Brillouin light-scattering measurements of the edge modes in an array of 480-nm-wide×12-nm-thick Ni80Fe20 stripes have a lower edge saturation field than the vertical edge models, but agree well with the model of 45°-tapered edges.