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Showing papers on "Saturation (magnetic) published in 2009"


Journal ArticleDOI
TL;DR: In this article, the formation of single-phase nickel ferrite nanoparticles in the range 8-28nm depending upon the annealing temperature of the samples during the synthesis was investigated.

390 citations


Journal ArticleDOI
TL;DR: A comparison of on-chip inductors with magnetic materials from previous studies is presented and examined in this article, where the inductors use copper metallization and amorphous Co-Zr-Ta magnetic material.
Abstract: A comparison of on-chip inductors with magnetic materials from previous studies is presented and examined. Results from on-chip inductors with magnetic material integrated into a 90 nm CMOS processes are presented. The inductors use copper metallization and amorphous Co-Zr-Ta magnetic material. Inductance densities of up to 1700 nH/mm2 were obtained thanks to inductance increases of up to 31 times, significantly greater than previously published on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. Co-Zr-Ta was chosen for its good combination of high permeability, good stability at high temperature (> 250degC), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The Co-Zr-Ta alloy can operate at frequencies up to 9.8 GHz, but trade-offs exist between frequency, inductance, and quality factor. Our inductors with thick copper and thicker magnetic films have dc resistances as low as 0.04 Omega, and quality factors of up to 8 at frequencies as low as 40 MHz.

306 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed an electrostatically tunable microwave multiferroic signal processing devices, including tunable resonators, phase shifters, and tunable filters.
Abstract: Multiferroic composite materials consisting of both a magnetic phase and a ferroelectric phase are of great current interest, as they offer the possibility ofmagnetoelectric (ME) coupling, that is, electric field manipulation of magnetic properties (converse ME effect) or vice versa (direct ME effect), and have led to many novel multiferroic devices. One important series of such multiferroic devices is constituted by electrostatically tunable microwave multiferroic signal processing devices, including tunable resonators, phase shifters, and tunable filters. Compared to conventional tunable microwave magnetic devices, which are tuned by magnetic fields, these electrostatically tunable microwave multiferroic devices are much more energy efficient, less noisy, compact, and lightweight. ME effects can be realized in multiferroic composites through a strain/stress-mediated interaction, which enables effective energy transfer between electric and magnetic fields and leads to important new functionalities and devices. Strong ME coupling is critical for multiferroic devices; however, it has been difficult to achieve at microwave frequencies, leading to a very limited tunability in electrostatically tunable microwave multiferroic devices. The demonstrated tunable range of most of these devices has been very limited, with a frequency tunability of Df< 150MHz and a low tunable magnetic field of DH< 50Oe (1 Oe 79.6 A m ). This is mainly due to the large loss tangents at microwave frequencies of the two constituent phases, that is, the ferroelectric phase and, particularly, the magnetic phase, which is less resistive. The ME coupling strength in multiferroic composites is determined by many factors, such as the properties of the two constituent phases, the interface between them, the mode of ME coupling, and the orientation of the magnetic and electric fields. As a result, layered multiferroic heterostructures with magnetic thin films provide great opportunities for achieving strong ME coupling at microwave frequencies, owing to minimized charge leakage paths and low loss tangents associated with magnetic thin films. It is also desirable for the magnetic phase in the multiferroic composites to have a narrow ferromagnetic resonance (FMR) linewidth and a large piezomagnetic coefficient (dl/dH), that is, a large saturation magnetostriction constant (ls) and a low saturation magnetic field (Hs). However, suchmagnetic materials have not been readily available. Very recently, we have reported a new class of metallic magnetic FeGaB films that has a high ls of ca. 70 ppm, a lowHs of ca. 20Oe, and a narrow FMR linewidth of ca. 16Oe at X-band (ca. 9.6GHz). The maximum piezomagnetic coefficient of the FeGaB films is about 7 ppm Oe , which is much higher than those of other well-known magnetostrictive materials used in multiferroic composites, such as Terfenol-D (Tb-Dy-Fe), Galfenol (Fe-Ga), and Metglas (FeBSiC), as shown in Figure 1. The combination of narrow FMR linewidth and high piezomagnetic coefficient makes these FeGaB films excellent candidates for the magnetic material in microwave multiferroic composites. Single-crystal ferroelectrics such as lead magnesium niobate–lead titanate (PMN-PT) and lead zinc niobate–lead titanate (PZN-PT) having giant piezoelectric coefficients and low loss tangents are desired for microwave multiferroic composites as well. In particular, (011)-cut PMN-PT and PZN-PT single-crystal slabs have anisotropic piezoelectric coefficients d31 and d32 when poled along their [011] crystalline direction. For example, (011)-cut PZN-PT single crystals with 6% lead titanate have high anisotropic piezoelectric coefficients d311⁄4 3000 pC N 1 and d321⁄4 1100 pC N . The giant anisotropic piezoelectric coefficients of the PZN-PTsingle crystal provide great opportunities for generating a large in-plane magnetic anisotropic field and

286 citations


Journal ArticleDOI
TL;DR: In this paper, magnetic flux measurements in seven rapidly rotating M dwarfs were made using near-infrared FeH molecular spectra observed with the High Resolution Echelle Spectrometer at Keck.
Abstract: We present magnetic flux measurements in seven rapidly rotating M dwarfs. Our sample stars have X-ray and Hα emission indicative of saturated emission, i.e., emission at a high level, independent of rotation rate. Our measurements are made using near-infrared FeH molecular spectra observed with the High Resolution Echelle Spectrometer at Keck. Because of their large convective overturn times, the rotation velocity of M stars with small Rossby numbers is relatively slow and does not hamper the measurement of Zeeman splitting. The Rossby numbers of our sample stars are as small as 0.01. All our sample stars exhibit magnetic flux of kG strength. We find that the magnetic flux saturates in the same regime as saturation of coronal and chromospheric emission, at a critical Rossby number of around 0.1. The filling factors of both field and emission are near unity by then. We conclude that the strength of surface magnetic fields remains independent of rotation rate below that; making the Rossby number yet smaller by a factor of 10 has little effect. These saturated M-star dynamos generate an integrated magnetic flux of roughly 3 kG, with a scatter of about 1 kG. The relation between emission and flux also has substantial scatter.

247 citations


Journal ArticleDOI
TL;DR: The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the faceted irregular cobalt ferrite nanostructure exhibit lower saturation magnetizations than their spherical counterparts.
Abstract: Cobalt ferrite magnetic nanostructures were synthesized via a high temperature solution phase method. Spherical nanostructures of various sizes were synthesized with the help of seed mediated growth of the nanostructures in the organic phase, while faceted irregular (FI) cobalt ferrite nanostructures were synthesized via the same method but in the presence of a magnetic field. Magnetic properties were characterized by superconducting quantum interference device (SQUID) magnetometry, relaxivity measurements, and thermal activation under RF field, as a function of size and shape. The results show that the saturation magnetization of the nanostructures increases with an increase in size, and the FI nanostructures exhibit lower saturation magnetization than their spherical counterparts. The relaxivity coefficient of cobalt ferrite nanostructures increases with an increase in size, while FI nanostructures show a higher relaxivity coefficient than spherical nanostructures with respect to their saturation magnet...

215 citations


Journal ArticleDOI
TL;DR: No evidence is found for any systematic variation of the electric or magnetic properties of BiFeO(3) depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.
Abstract: We have synthesized a range of transition-metal-doped BiFeO3 thin films on conducting silicon substrates using a spin-coating technique from metal–organic precursor solutions. Bismuth, iron and transition-metal–organic solutions were mixed in the appropriate ratios to produce 3% transition-metal-doped samples. X-ray diffraction studies show that the samples annealed in a nitrogen atmosphere crystallize in a rhombohedrally distorted BiFeO3 structure with no evidence for any ferromagnetic secondary phase formation. We find evidence for the disappearance of the 404 cm−1 Raman mode for certain dopants indicative of structural distortions. The saturation magnetization of these BiFeO3 films has been found to increase on doping with transition metal ions, reaching a maximum value of 8.5 emu cm−3 for the Cr-doped samples. However, leakage current measurements find that the resistivity of the films typically decreases with transition metal doping. We find no evidence for any systematic variation of the electric or magnetic properties of BiFeO3 depending on the transition metal dopant, suggesting that these properties are determined mainly by extrinsic effects arising from defects or grain boundaries.

134 citations


Journal ArticleDOI
TL;DR: In this article, the properties of Gd and Nd-substituted nickel ferrite were investigated and the existence of the ferroelectricity was confirmed from the Ferroelectric loops and magnetocapacitance of −2% and −3% were observed.

122 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical model to represent the 3D magnetic flux leakage (MFL) field due to the occurrence of a surface-breaking defect in a ferromagnetic specimen is presented.
Abstract: In this paper, we present an analytical model to represent the 3-D magnetic flux leakage (MFL) field due to the occurrence of a surface-breaking defect in a ferromagnetic specimen. This situation is frequently encountered in the nondestructive evaluation (NDE) of energy pipelines using the MFL technique. The model is derived from first principles, and utilizes the concept of dipolar magnetic charge induction to yield the 3-D MFL field in terms of surface integrals. The magnetic flux density in the specimen is assumed to be in the saturation region, and the permeability is assumed to be locally constant in the vicinity of the defect. The model uses just two geometric parameters and is capable of reproducing results that have been obtained experimentally in the literature. 3-D MFL field simulations obtained from the model facilitate a better understanding of the effect of a surface-breaking defect on the magnetic field in its vicinity. Furthermore, we simulate and analyze the 3-D MFL field in the 3-D space around the defect. This analysis yields numerous properties regarding the spatial characteristics of the three orthogonal components of the MFL field of the defect.

119 citations


Journal ArticleDOI
TL;DR: In this paper, magnetic nanoparticles of nickel substituted cobalt ferrite (Ni x Co 1− x Fe 2 O 4 :0≤ x ≤ 1) have been synthesized by co-precipitation route.
Abstract: Magnetic nanoparticles of nickel substituted cobalt ferrite (Ni x Co 1− x Fe 2 O 4 :0≤ x ≤1) have been synthesized by co-precipitation route. Particles size as estimated by the full width half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak and transmission electron microscopy (TEM) techniques was found in the range 18–28±4 nm. Energy dispersive X-ray (EDX) analysis confirms the presence of Co, Ni, Fe and oxygen as well as the desired phases in the prepared nanoparticles. The selective area electron diffraction (SAED) analysis confirms the crystalline nature of the prepared nanoparticles. Data collected from the magnetization hysteresis loops of the samples show that the prepared nanoparticles are highly magnetic at room temperature. Both coercivity and saturation magnetization of the samples were found to decrease linearly with increasing Ni-concentration in cobalt ferrite. Superparamagnetic blocking temperature as determined from the zero field cooled (ZFC) magnetization curve shows a decreasing trend with increasing Ni-concentration in cobalt ferrite nanoparticles.

119 citations


Journal ArticleDOI
TL;DR: In this paper, X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), and vibrating scanning magnetometry (VSM) were used for the structural, morphological, and magnetic characterizations of the product.

118 citations


Journal ArticleDOI
TL;DR: A simple model is proposed here to explain the behavior of microrod-based MR fluids at low, medium and saturating magnetic fields in the viscoelastic linear regime in terms of magnetic interaction forces between particles.
Abstract: The effect of particle shape in the small amplitude oscillatory shear behavior of magnetorheological (MR) fluids is investigated from zero magnetic field strengths up to 800 kA/m. Two types of MR fluids are studied: the first system is prepared with spherical particles and a second system is prepared with rodlike particles. Both types of particles are fabricated following practically the same precipitation technique and have the same intrinsic magnetic and crystallographic properties. Furthermore, the distribution of sphere diameters is very similar to that of rod thicknesses. Rod-based MR fluids show an enhanced MR performance under oscillatory shear in the viscoelastic linear regime. A lower magnetic field strength is needed for the structuration of the colloid and, once saturation is fully achieved, a larger storage modulus is observed. Existing sphere- and rod-based models usually underestimate experimental results regarding the magnetic field strength and particle volume fraction dependences of both storage modulus and yield stress. A simple model is proposed here to explain the behavior of microrod-based MR fluids at low, medium and saturating magnetic fields in the viscoelastic linear regime in terms of magnetic interaction forces between particles. These results are further completed with rheomicroscopic and dynamic yield stress observations.

Journal ArticleDOI
TL;DR: In this article, NiFe2O4 nano-particles were synthesized by a simple and cost-effective method using Ni and Fe nitrates and glycine, which showed significant effect of the ratio between glycine and nitrates on the physical parameters like crystalline phase, crystallite size, and particle size, lattice constant and magnetic properties of the nanoparticles.

Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of ferrimagnetic and non-interacting hollow nanoparticles obtained by the Kirkendall effect were investigated in terms of the microstructural parameters characterizing the maghemite shells by means of atomistic Monte Carlo simulations of an individual spherical shell.
Abstract: In the present work, we investigate the magnetic properties of ferrimagnetic and non-interacting maghemite hollow nanoparticles obtained by the Kirkendall effect. From the experimental characterization of their magnetic behavior, we find that polycrystalline hollow maghemite nanoparticles exhibit low blocked-to-superparamagnetic transition temperatures, small magnetic moments, significant coercivities and irreversibility fields, and no magnetic saturation on external magnetic fields up to 5 T. These results are interpreted in terms of the microstructural parameters characterizing the maghemite shells by means of atomistic Monte Carlo simulations of an individual spherical shell. The model comprises strongly interacting crystallographic domains arranged in a spherical shell with random orientations and anisotropy axis. The Monte Carlo simulation allows discernment between the influence of the polycrystalline structure and its hollow geometry, while revealing the magnetic domain arranggement in the different temperataure regimes.

Journal ArticleDOI
TL;DR: By investigating the axial fluctuations of DNA-bound microspheres, it is found that considerable rotational microsphere fluctuations can occur and Quantitative noise analysis allowed us to determine the rotational stiffness of individual micro spheres, which was found to saturate at high magnetic fields.
Abstract: We used magnetic tweezers to measure the torsional stiffness of single micrometer-sized superparamagnetic spheres as a function of the applied magnetic field. By investigating the axial fluctuations of DNA-bound microspheres, we found that considerable rotational microsphere fluctuations can occur. Quantitative noise analysis allowed us to determine the rotational stiffness of individual microspheres, which was found to saturate at high magnetic fields. The saturation can be qualitatively explained considering the properties of the magnetic nanoparticles within the microsphere. Consequences for spatial resolution limits in single-molecule magnetic tweezer experiments and usage of DNA mechanics as a sensitive probe in magnetometry are discussed.

Journal ArticleDOI
TL;DR: In this paper, the structural relationship between Co3Sn2S2 and the intermetallic compound CoSn, both of which contain Kagome nets of cobalt atoms, is discussed.

Journal ArticleDOI
15 Aug 2009
TL;DR: By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500 degrees C, this method thus stabilizes the hcp cobalt even at sizes (<10 nm) at which normally fcc cobalt is predicted to be stable.
Abstract: By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500 degrees C. This method thus stabilizes the hcp cobalt even at sizes (<10 nm) at which normally fcc cobalt is predicted to be stable. On annealing the hcp cobalt nanoparticles in H-2 at 700 degrees C we could transform them to fcc cobalt nanoparticles. Microscopy studies show the formation of spherical nanoparticles of hexagonal and cubic forms of cobalt and Co-Ni (1:1) alloy nanoparticles with the average size of 4, 8 and 20 nm, respectively. Electrochemical studies show that the catalytic property towards oxygen evolution is dependent on the applied voltage. At low voltage (less than 0.65 V) the Co (hexagonal) nanoparticles are superior to the alloy (Co-Ni) nanoparticles while above this voltage the alloy nanoparticles are more efficient catalysts. The nanoparticles of cobalt (hcp and fcc) and alloy (Co-Ni) nanoparticles show ferromagnetism. The saturation magnetization of Co-Ni nanoparticles is reduced compared to the bulk possibly due to surface oxidation.

Journal ArticleDOI
TL;DR: In this article, the mixed spinel phases of the nanocrystalline materials have been confirmed by X-ray diffractograms (XRD) and the sizes of the nanoparticles are estimated from the (3 − 1 1) peaks of the XRD patterns using Debye-Sherrer equation.

Proceedings ArticleDOI
21 Mar 2009
TL;DR: In this paper, the authors present analytical and experimental comparisons of the magnetic materials used in a practical dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range and the low (1% to high(220%) current ripple range.
Abstract: Dc-dc converter size and efficiency are driving factors in industrial, aerospace and automotive applications. Thus, optimal component selection is essential for a compact design. The inductor often appears as the converter's largest component. This paper presents analytical and experimental comparisons of the magnetic materials used in a practical design. The investigation is concerned with magnetic material selection for a dc-dc power inductor in the medium (20 kHz) to high (150 kHz) frequency range and the low (1%) to high (220%) current ripple range. The materials under investigation are iron-based amorphous metal, silicon steel, nanocrystalline, ferrite, powdered iron and gap-less powder materials. A newly developed silicon steel material from JFE-Steel Co. is presented. A novel material comparison which includes thermal conductivity and saturation capability is proposed. The area product analysis for material comparison is presented for 10 kW dc-dc inductor design examples. The variation of core power loss with dc-bias is experimentally investigated for different materials. A 1.25 kW half-bridge dc-dc converter is used in experimental validation.

Journal ArticleDOI
TL;DR: In this paper, the authors considered the case of very weak or zero mean magnetic field, which is applicable to the turbulence in the intergalactic space, and presented a formula that expressed the standard deviation of RM, sigma{sub RM, in terms of the integral scale and rms strength of the IGMF, and estimate that sigma-sub RM would be approx100 and approx a few rad m{sup -2} for clusters and filaments, respectively.
Abstract: In the framework of turbulence dynamo, flow motions amplify a weak seed magnetic field through the stretching of field lines. Although the amplification process has been a topic of active research, less attention has been paid to the length scales of magnetic field. In this Letter, we describe a numerical study on characteristic lengths of magnetic field in magnetohydrodynamic turbulence. We considered the case of very weak or zero mean magnetic field, which is applicable to the turbulence in the intergalactic space. Our findings are as follows. (1) At saturation, the peak of magnetic field spectrum occurs at approxL{sub 0}/2, where L{sub 0} is the energy injection scale, while the most energy containing scale is approxL{sub 0}/5. The peak scale of spectrum of projected, two-dimensional field is approxL{sub 0}. (2) During the stage of magnetic field amplification, the energy equipartition scale shows a power law increase of approxt {sup 1.5}, while the integral and curvature scales show a linear increase. The equipartition, integral, and curvature scales saturate at approxL{sub 0}, approx0.3L{sub 0}, and approx0.15L{sub 0}, respectively. (3) The coherence length of magnetic field defined in the Faraday rotation measure (RM) due to the intergalactic magnetic field (IGMF) is related tomore » the integral scale. We present a formula that expresses the standard deviation of RM, sigma{sub RM}, in terms of the integral scale and rms strength of the IGMF, and estimate that sigma{sub RM} would be approx100 and approx a few rad m{sup -2} for clusters and filaments, respectively.« less

Journal ArticleDOI
TL;DR: In this paper, the structural, thermal and magnetic properties of synthesized powder particles have been studied as a function of calcination temperature, and the presence of functional group was identified by Fourier transform infrared (FTIR) spectroscopic studies.

Journal ArticleDOI
TL;DR: In this article, the effect of adding polyethylene glycol (PEG 2000) into the sol solutions of Ba-M-type hexagonal ferrites has been studied.

Journal ArticleDOI
TL;DR: In this paper, the augmented spherical wave method has been used to calculate the electrical resistivity and thermoelectric power of CuCrO2 for the delafossite structure.

Journal ArticleDOI
TL;DR: In this article, transport, thermal, and magnetic measurements on single crystalline samples of FeGa 3 prepared by a Ga self flux method were reported, showing that the diamagnetic susceptibility weakly depends on temperature, which confirms the absence of localized magnetic moments.
Abstract: We report transport, thermal, and magnetic measurements on single crystalline samples of FeGa 3 prepared by a Ga self flux method. The electrical resistivity and Hall coefficient at temperatures above 300 K display semiconducting behaviors with energy gaps of 0.47 and 0.54 eV, respectively, whose values agree with the calculated band gap. In the saturation range 100–260 K, the carrier mobility µ exhibits an unusual dependence on temperature; µ( T )∝ T -5/2 . The thermopower has a large negative minimum of -350 µV/K at 300 K. The diamagnetic susceptibility weakly depends on temperature, which confirms the absence of localized magnetic moments. The T -linear coefficient of the specific heat is 0.03 mJ/(K 2 ·mol), being two orders of magnitude smaller than that reported for Fe-based Kondo semiconductors FeSi and FeSb 2 .

Journal ArticleDOI
TL;DR: In this article, the structural and magnetic properties of magnetic Fe3O4 nanoparticles are studied by means of X-ray diffraction, transmission electron microscopy (TEM), Raman spectrum, Fourier Transform Infrared (FT-IR), and a Vibrating Sample Magnetometer (VSM).
Abstract: Magnetic Fe3O4 nanoparticles are prepared by the coprecipitation method and coated with starch as a surfactant. Their structural and magnetic behaviours are studied by means of X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Raman spectrum, Fourier Transform Infrared (FT-IR) as well as with a Vibrating Sample Magnetometer (VSM). The magnetic Fe3O4 nanoparticles under investigation have an average size of about 14 nm. The coated magnetic nanoparticles exhibit super-paramagnetic behaviours with a blocking temperature of about 170 K and saturation magnetisation ranging between 30 and 50 emu g−1. In addition, the results of FT-IR indicated that interactions between the Fe3O4 particles and starch layers are much improved.

Journal ArticleDOI
TL;DR: In this article, the fabrication process, magnetic behavior, as well as the surface modification of ferromagnetic microdisks suspended in aqueous solution are described, and a successful attempt to bind thiolates including SH-modified antibody, to the disk's surface was demonstrated.
Abstract: We report the fabrication process, magnetic behavior, as well as the surface modification of ferromagnetic microdisks suspended in aqueous solution. They posses unique properties such as high magnetization of saturation, zero remanence due to spin vortex formation, intrinsic spin resonance at low frequencies, and the capability of delivering various biomolecules at once. Furthermore, because of their anisotropic shape, our magnetic particles rotate under alternating magnetic fields of small amplitude. This can be used to promote the idea of advanced therapies, which include combined drug delivery and magnetomechanical cell destruction when targeting tumor cells. The approach enables us to fabricate suitable magnetic carriers with excellent size tolerances, and then release them from the wafer into solution, ready for surface modification and therapeutic use. The particles have a magnetic core and are covered with few nanometers of gold on each side to provide stability at ambient conditions as well as biocompatibility and selective adhesion functions. A successful attempt to bind thiolates, including SH-modified antibody, to the disk’s surface was demonstrated.

Journal ArticleDOI
TL;DR: In this paper, two-dimensional handkerchief-like nanostructures of Ni and NiCo magnetic amorphous alloys have been synthesized by a double composite structure-inducing template.
Abstract: Two-dimensional handkerchief-like nanostructures of Ni and NiCo magnetic amorphous alloys have been synthesized by a double composite structure-inducing template. High resolution transmission electron microscopy was used to characterize the morphology and the dimensions. The self-assembly of fine handkerchief-like Ni and NiCo nanoalloys is attributed to the cooperation between ion-selected delivery of a hard collodion membrane by nitro-group chemical complexations and the size-controlled action of a reverse microemulsion. Importantly, the coordinations of ethylenediamine with Ni2+ and Co2+ can restrict the structure-inducing action. The phase transformation behavior was recorded by differential scanning calorimetry. Substituting Co for Ni can slow phase transformation, and the kinetic ordering temperature increases with the Co concentration increasing. The magnetic property measurement results show that the saturation magnetizations increase as the Co concentration is increased, but the coercivity is not ...

Journal ArticleDOI
TL;DR: In this paper, the effect of Ni concentration on magnetic properties such as saturation magnetization and Curie temperature were investigated and a good knowledge of these magnetic properties is desirable from application point of view.

Journal ArticleDOI
Yao-Zu Zhang1, Litao Sun1, Yu Fu1, Zhaocong Huang1, Xiaowan Bai1, Ya Zhai1, J. Du1, H. R. Zhai1 
TL;DR: In this paper, a series of Fe3O4 particle chains with an average particle diameter of 150 nm and different lengths were synthesized by using the self-assembly method at reduced temperature in different synthesizing magnetic fields.
Abstract: A series of Fe3O4 particle chains with an average particle diameter of 150 nm and different lengths were synthesized by using the self-assembly method at reduced temperature in different synthesizing magnetic fields. The influence of synthesizing magnetic field on the properties of the magnetite particle chains was studied by structural analyses, magnetometry measurement, and ferromagnetic resonance. A uniaxial magnetic anisotropy in the saturation field (Hs), hysteresis loop, and ferromagnetic resonance were observed to increase with increasing synthesizing field. The saturation magnetization and g-factor were found to increase slightly with increasing synthesizing field. The demagnetizing fields and demagnetizing factors were determined from the experimental data of magnetometry measurement, ferromagnetic resonance, and also numerical calculation, which agreed reasonably well. It was found that the magnetization non-uniformity in the chains and the magnetostatic interaction among the chains have an impo...

Journal ArticleDOI
TL;DR: In this paper, polycrystalline Fe 100− x Ga x (19⩽ x ⩽23) films were grown on Si(1/0/0) substrates at different partial pressures of sputtering gas ranging from 3 to 7μbar.

Journal ArticleDOI
TL;DR: In this paper, the frequency dependent microwave response of 40 nm diameter CoFeB ferromagnetic nanowire arrays, with external static applied field parallel to the nanowires axis, was determined for applied fields below and above magnetization saturation.
Abstract: Microstrip line measurements are used to determine the frequency dependent microwave response of 40 nm diameter CoFeB ferromagnetic nanowire arrays, with external static applied field parallel to the nanowire axis. The ferromagnetic resonance (FMR) response of the wires is obtained for applied fields below and above magnetization saturation. For applied magnetic fields above saturation, a single FMR peak is observed, while below saturation, two sets of peaks are obtained. The two FMR peaks below saturation are associated with two magnetization populations, one for nanowires with upward magnetization and one with downward magnetization. A model based on a Maxwell–Garnett homogenization procedure has been established and used to predict the frequency response of the FMR peaks. There is good agreement between the model and experimental results.