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Magnetics, IEEE Transactions on

Issue 5 • Date Sep 1996

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Displaying Results 1 - 25 of 283
  • The residual amorphous phase in nanocrystalline soft magnetic FeSiCuNbB

    Page(s): 4881 - 4883
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    In order to synthesize separately the residual amorphous phase present in rapidly quenched nanocrystalline FeSiCuNbB ribbons, powders of nominal composition Fe92-xNb8Bx with x=19...45 as well as Fe63Nb9B28 and Fe 55Nb12B33 were mechanically alloyed for amorphization and annealed at 540°C for structural relaxation. The amorphous powder products show crystallization temperatures Tx1 and Tx2 increasing with B content from 600 to 750°C and 750 to 950°C respectively. The Curie temperature and also room-temperature saturation polarization show maximum values of about 140°C and 0.8 T at a B content of 25 at.%. Compared to that, the Curie temperature of the amorphous grain boundary phase of same composition in nanocrystalline FeSiCuNbB is by at least 100°C higher, presumably caused by exchange-field penetration from the adjacent α-FeSi nanocrystallites View full abstract»

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  • Torsion and stress in amorphous positive magnetostrictive wires

    Page(s): 4953 - 4955
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    In this paper we report some results on the dependence of the pulsed voltage output on the applied torsion or tensile stress in Fe77.5Si7.5B15 amorphous wires used as magnetostrictive delay lines. The obtained results show a non monotonic dependence of the response of the delay line on applied torsion. For applied tensile stress the response could be fitted by a linear curve for as-cast wires and by an exponential curve for annealed wires. The good ratio between minimum and maximum magnetostrictive delay line signals and the absence of hysteresis suggest the possibility to use this technique in load cells and torque sensors View full abstract»

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  • Magnetic permeability measurements in GMR multilayers with extra-thick magnetic layers

    Page(s): 4681 - 4683
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    Initial permeability and transverse bias permeability measurements have been made on [NiFeCo(t)/Cu(23 Å)]16 multilayers for different magnetic layer thicknesses(t) in the as-deposited state and after an annealing treatment. The initial permeability was found to be independent of frequency up to at least 100 MHz and to increase with magnetic layer thickness. The transverse bias permeability is used to calculate the effective uniaxial anisotropy and the bilinear and biquadratic exchange fields. The thicker multilayers are found to be ferromagnetically coupled in the as-deposited state and upon annealing a transition occurs producing antiferromagnetically coupled magnetic layers View full abstract»

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  • Enhancement of giant magneto-impedance in layered film by insulator separation

    Page(s): 4965 - 4967
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    Giant Magneto-Impedance (MI) effect of CoSiB/SiO2/Cu/SiO2/CoSiB films with line structures have been studied. Easy axes have been induced in perpendicular direction to the driving current, and the insulating SiO 2 layers have prevented the driving current from penetrating into the CoSiB layers. This structure has enabled the effective occurrence of resistance change at a frequency as low as several MHz. As a result, impedance change ratios ΔZ/Z0=(Zmaximum -Z(Hext=0))/Z(Hext=0) are much higher than that of any other layered film without insulating layers. The ΔZ/Z 0 at 20 MHz is as high as 700% at 11 Oe, and the maximum slope is 300%/Oe View full abstract»

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  • A new field-sensing method to measure the power loss of electrical steel sheet under two-dimensional measuring conditions

    Page(s): 4908 - 4910
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A sensor system is proposed that allows a fast and integral measurement of the power loss in the sample volume independent of the geometry and positioning of the sample in the setup. The power loss is determined under various two-dimensional measuring conditions. The obtained values are compared to those investigated with standard methods View full abstract»

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  • Finite element simulation of magnetic detection of creep damage at seam welds

    Page(s): 4290 - 4292
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    Using appropriately modified magnetization curves for each element of creep-damaged material, a finite element calculation has been carried out to simulate magnetic detection of non-uniform creep damage around a seam weld in a 2.25 Cr 1 Mo steam pipe. The magnetization curves for the creep-damaged elements were obtained from an earlier model for the magnetic effect of a uniformly creep-damaged material as given by Chen, et al. In the finite clement calculation, a magnetic C-core with primary and secondary coils was placed with its pole pieces flush against the specimen in the vicinity of the weld. The secondary emf was shown to be reduced when creep damage was present inside the pipe wall at the cusp of weld and in the vicinity of the cusp. The C-core detected the creep damage best if it completely spanned the weld seam width. Also, the current in the primary needed to be such that the C-core was not magnetically saturated View full abstract»

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  • Time-dependent magnetic behaviour of Ba ferrite particles at low temperature

    Page(s): 4517 - 4519
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    The time dependence of the magnetization of pure and Co/Ti-doped Ba ferrite particles is analysed at low temperatures and compared with the dependence at room temperature. In undoped particles the variation of the magnetization and the magnetic viscosity are smaller at low than at room temperature, as expected from the increase of thermal stability of the magnetization with the decrease of temperature. On the contrary, in Co/Ti-doped particles for magnetic recording media, we observe an anomalous increase of the magnetization variation during the time and of magnetic viscosity when the temperature decreases. This behaviour is interpreted on the basis of the evolution of magnetic anisotropy with the temperature in doped Ba ferrite particles, where the magnetocrystalline anisotropy at low temperature becomes comparable with the shape anisotropy View full abstract»

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  • Sputtered NiFeZr as a soft biasing layer in MR head

    Page(s): 4526 - 4528
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    The sputtered soft magnetic NiFeZr films were studied experimentally for the use as a soft adjacent layer (SAL) in magnetoresistive (MR) heads. The influence of the film thickness and sputtering conditions on the magnetic and electrical properties of the films was investigated. The coercivity HC and the anisotropy field HK considerably depends on the substrate temperature T S during the deposition. The films of the thickness below 400 Å have the following properties: HC<0.5 Oe, HK <6 Oe, a resistivity ρ=91 μOhm·cm, a magnetoresistance ratio Δρ/ρ<0.05%, a saturation induction Bs=0.65 T, and a magnetostriction constant λ s=4×10-7. The films exhibit stable amorphous structure. The above results show that sputtered NiFeZr films emerge as a good candidate for SAL in MR heads. Some characteristics of three-layered (NiFeZr/Ta/NiFe) MR elements have also been discussed in this paper View full abstract»

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  • A detection of backside crack using rotational magnetic flux sensor with search coils

    Page(s): 4968 - 4970
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    We have developed a new magnetic sensor using a rotational magnetic field with a three-axis search coil for non-destructive testing (NDT). Using specimens with a machined crack in the center, we investigated the relationship between the position end the depth of a crack and the output signal of the three-axis search coil. The results of our experiments, this sensor can clearly detect a crack existing on the reverse side of the sensing surface. In this paper, we present the construction, results of numerical analysis and experimental results of this sensor View full abstract»

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  • Harmonic analysis of AC magnetostriction measurements under non-sinusoidal excitation

    Page(s): 4911 - 4913
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A new system for analyzing ac magnetostriction of electrical steel sheets, has been developed. This system has the following advantages: (a) AC magnetostriction waveforms can be precisely measured up to 4 kHz, and analyzed to harmonic components. (b) Non-sinusoidal flux density can be excited to simulate the distorted waveform in an actual transformer core View full abstract»

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  • Interaction domains in isotropic, fine-grained Sm2Fe17N3 permanent magnets

    Page(s): 4362 - 4364
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    The magnetization process in fine grained Sm2Fe17 N3 permanent magnets were studied with high resolution Kerr microscopy and measurements of the magnetization curves. Different susceptibilities after thermal and DC-demagnetization were observed for HDDR processed samples but not for long milled material. The differences for the HDDR material are interpreted considering cooperative magnetization phenomena (`interaction domains') that produce changes in the degree of frustration between the magnetization directions of neighbouring grains View full abstract»

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  • Field distribution and power loss assessment in conductive rod cores exhibiting hysteresis

    Page(s): 4293 - 4295
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Recently, a new numerical approach for core loss evaluation in media exhibiting hysteresis has been proposed for relatively long conductive rods, subject to surface excitation along their azimuthal direction. In this approach, the Crank-Nicolson finite-difference technique is used, while enact media properties are taken into account by utilizing Preisach-type models of hysteresis. The purpose of this paper is to provide some experimental verification of the aforementioned approach. Accuracy of this approach has been assessed for a 2 cm diameter, 25 cm long iron alloy rod. Voltage wave-forms and core losses corresponding to some controlled applied field frequencies and amplitudes were experimentally deduced. For every experimentally considered excitation amplitude and frequency, computations were performed rising the developed approach. Comparisons have demonstrated good quantitative agreements between the experimentally measured computed results. Sample comparison results are given in the paper View full abstract»

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  • Investigation of the gyromagnetic permeability of amorphous CoFeNiMoSiB manufactured by different techniques

    Page(s): 4833 - 4835
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    The permeability of amorphous non-magnetostrictive flexible ferromagnetic films is investigated in the 10 MHz to 1.6 GHz range. The permeability of melt-spun ribbons is shown to increase after chemical thinning, but no improvement is seen concerning losses in this frequency range. It is shown that demagnetizing fields affect the measured permeability, either because of finite sample size effects, or because of thickness inhomogeneities. Thinner layers were manufactured by ion beam sputtering using the melt spun ribbons as targets. Real permeability levels of 500 and resonance frequencies close to 1 GHz are observed on the layers sputtered on Kapton as well as on that sputtered on glass substrates. After annealing, flexible material with initial permeability higher than 1500 and resonance frequency of 530 MHz is produced. The study of the permeability on a broad frequency range indicates that the occurrence of high frequency losses in the hundred MHz range is-due not to skin effect but to intrinsic damping of the gyromagnetic resonance View full abstract»

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  • Distributions on localized iron loss of three-phase amorphous transformer model core by using two-dimensional magnetic sensor

    Page(s): 4797 - 4799
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    In the past, we reported on the two-dimensional magnetic properties of the three-phase transformer model core with silicon iron. They are measured by using the two-dimensional magnetic sensor. In this paper, the silicon iron core results are compared with those of an amorphous power core. As the results, the differences between the two materials are made clear View full abstract»

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  • The use of Co79Cr21 undercoats for controlling the soft magnetic properties of RF sputtered Permalloy thin films

    Page(s): 4520 - 4522
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    The effects of Co79Cr21 undercoats and nucleating layers on the coercive force, anisotropy field, and 5 MHz to 100 MHz complex permeability spectra of magnetically soft, Ni81 Fe19 thin films RF sputtered onto glass substrates are investigated. While very thin layers of HCP oriented Co79Cr 21≈5 nm, do not affect the coercive force of the NiFe layer, they do increase the measured anisotropy. Thicker CoCr layers increase both the coercive force and anisotropy field. The 5 nm layers of Co79Cr21 act to increase the magnitude of the μ' spectra, μ=μ'-jμ", while decreasing the μ" spectra; thicker layers of CoCr reduce both μ' and μ" View full abstract»

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  • High current density self-field effects and low-frequency noise in NiFe/Ag GMR multilayers

    Page(s): 4684 - 4686
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    High current densities (106-107 A/cm2 ) produce magnetic fields which can induce antiparallel magnetic alignment in large (16 μm and 8 μm) NiFe/Ag thin film multilayer devices. We induce GMR in unannealed devices which normally do not display GMR. We find multiple peaks in the magnetoresistance curves of annealed and unannealed devices. Analysis of the positions and shapes of these magnetoresistance peaks provides a new set of tools for determining the micromagnetic structure of the multilayers. Our magneto-optical Kerr effect data and low frequency noise data correlate with the magnetoresistance peaks and may yield further information about layer-layer interactions and domain structure View full abstract»

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  • Hetero-amorphous Fe-Co-B-C soft magnetic thin films with uniaxial magnetic anisotropy and large magnetostriction

    Page(s): 4529 - 4531
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    Hetero-amorphous (Fe0.75Co0.25)1-x(B1-yC y)x films have been obtained by RF magnetron sputtering. Magnetic properties strongly depended on the hetero-amorphous substructure of the films. The film with a fine substructure less than 10 nm in mean diameter exhibited low coercive force of 40 A/m along the hard axis, large spontaneous magnetization of 1.6 T, and in-plane anisotropy field of 1.2 kA/m induced by field-annealing although the film had a large magnetostriction constant of 39×10-6 View full abstract»

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  • Magnetoresistance characteristics of (NiFe/Ni/NiFe)/Cu multilayers

    Page(s): 4725 - 4727
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    By inserting two or three layers of NiFe at the interfaces of Ni/Cu multilayers, the magnetoresistance properties of Ni/Cu could be appreciably improved. 50 Oe of saturation magnetic field and 6% of magnetoresistance were obtained in glass/Cu(50 Å)[NiFe(7 Å)Ni(6 Å)NiFe(7 Å)/Cu(20 Å)]20 structured multilayers. 25 Oe of saturation magnetic field and 4.5% of magnetoresistance were obtained in 4° tilt-cut Si(111)/NiFe(50 Å)[NiFe(7 Å)Ni(6 Å)NiFe(7 Å)/Cu(20 Å)]10. Almost negligible hysteresis was shown in both structures, which turned out to be much advantageous in obtaining magnetoresistance signals under ac magnetic field View full abstract»

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  • The magnetic properties of ultrathin Fe-Al-Nb-B-Cu nanocrystalline alloys

    Page(s): 4830 - 4832
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    The magnetic properties of ultrathin Fe75Al4Nb5B12Cu1 nanocrystalline alloy ribbons with 9 μm thickness and the effect of Al additions to Fe-B-Nb-Cu alloy for improving the high-frequency magnetic properties were investigated. It was found that the effective permeability at frequencies over 100 kHz was higher and the core loss was lower for the composition Fe75Al4Nb5B12Cu1 alloy. Moreover, the reduction of the ribbon thickness to 9 μm was very effective in improving their permeability and the core loss characteristics up to the MHz frequency range View full abstract»

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  • Magnetic properties of sequentially sputtered amorphous Fe-Ge thin films

    Page(s): 4538 - 4540
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    FexGe100-x films with compositions in the range 50⩽x⩽82 at 300 K were deposited by rf diode, sequential sputtering from elemental targets. All the films were amorphous at 300 K indicating that the Fe concentration in the stable amorphous films was increased by more than 10 at. % over that obtained by vapor deposition. The sequentially sputtered Fe-Ge films exhibited a heteroamorphous morphology with nanoscale features that varied with composition. The variations in the 4πMs and Tc for the sputtered Fe rich films, agreed well with data extrapolated from measurements on Ge rich evaporated films. The improvement in the soft magnetic properties produced in these films by rotating magnetic field annealing (RFA) was shown to be correlated with changes in film morphology View full abstract»

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  • Interlayer coupling in spin valve structures

    Page(s): 4642 - 4644
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    The effect of structural imperfections such as interface roughness and layer strain on the sign and amplitude of the interlayer coupling between the two ferromagnetic layers of exchanged-biased NiFe/Cu/NiFe/FeMn spin valves is discussed. Two distinct regimes are found: when the NiFe-Cu interface is smooth, with a mean roughness smaller that 4 Å, the interlayer coupling shows a distinct oscillatory behavior, with a period of Λ=13.5 Å, and can be well described by a RKKY-like exchange based mechanism. As the amplitude of the interface roughness increases the magnetostatic-type Neel's orange peel coupling becomes more important, and the ferromagnetic component of the coupling is enhanced. The higher than expected period of oscillation, observed in these spin valves, is explained in terms of a strain induced effect View full abstract»

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  • Study of thermal decomposition mechanism of the Fe17Sm 2N3 phase

    Page(s): 4365 - 4367
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    We studied the high temperature decomposition mechanism for the Fe 17Sm2N phase using several different experimental techniques, as thermomagnetic and thermogravimetric analyses. Our results show that the decomposition occurs in a two step scheme. In the first reaction we hare the formation of SmN and a solid solution of nitrogen in iron. In the second step, this solid solution degases, and we observe the evolution of nitrogen over a broad temperature range View full abstract»

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  • Numerical method for estimating the electromagnetic parameters of shielding materials

    Page(s): 4296 - 4298
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    This paper presents an approach to estimate the electromagnetic parameters of shielding materials at low frequencies based upon shielding measurements. The method is applied to compute the electric conductivity and magnetic permeability of several long cylinders which are made of aluminum, Amumetal, and Conetic-AA, respectively. The results are consistent with their published data and show the application potential of the method View full abstract»

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  • Signal transmission for implantable medical devices using figure-of-eight coils

    Page(s): 5121 - 5123
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    A new skin-transparent signal transmission method is proposed. For applications on high energy-consumption medical devices such as total artificial hearts or implantable FES (functional electrical stimulation) systems, we constructed a transcutaneous signal transmission system using figure-of-eight coils, as it is apparent that these applications need feedback and/or controlling signals for stable and safe operation. By employing figure-of-eight coils, we could reduce noise coming from around the coil and still suppress noise emitted from the transmitting coil. In the animal experiment using a goat, we could successfully observe the fluctuation in the amount of the transmitted energy through skin with figure-of-eight coils of 30 mm in diameter. Meanwhile, figure-of-eight coils didn't cause any unfavorable interferences with the electromagnetically driven ventricular assist device connected to the goat's heart at the time View full abstract»

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  • Colossal magnetoresistance in La-Y-Ca-Mn-O films

    Page(s): 4692 - 4694
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    Magnetoresistance behavior of La0.60Y0.07CaMnOx thin films epitaxially grown on LaAlO3 has been investigated. The films exhibit colossal magnetoresistance with the MR ratio in excess of 108% at -60 K, H=7T, which is the highest ever reported for thin film manganites. The partial substitution of La3+ ions with much smaller Y3+ ions results in mote than an order of magnitude improvement in MR as compared to the undoped La-Ca-Mn-O material, both in bulk and thin film form. The La-Y-Ca-Mn-O films exhibit a strong dependence of magneto-resistance on film thickness with the maximum MR occuring at a film thickness of -1000 View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology