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Magnetics, IEEE Transactions on

Issue 4 • Date July 1976

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Displaying Results 1 - 23 of 23
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Contributions of rock magnetism and paleomagnetism to recent geophysical advances

    Page(s): 266 - 278
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    The origin of natural remanent magnetization (NRM) in rocks is discussed both in terms of types and carriers of NRM. The importance of the concept of pseudo-single domain (PSD) grains as carriers of stable remanences is underscored. Recent advances in rock magnetism and paleomagnetism have helped to understand (a) continental motions which took place in the first 4 billion years of the earth's life, (b) fine details of field fluctuations both during "normal" times as well as during a geomagnetic field reversal, and (c) indicate the magnitudes of the fields present during the formation of the moon and of the early solar system. View full abstract»

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  • The invar problem

    Page(s): 278 - 291
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    The purpose is to make clear the fundamental physical nature of the Invar problem, disregarding its details. After a brief discussion of the practical applications of the Invar alloys, the large magnetovolume effects and the anomalous magnetic properties are reviewed. The basic ideas of the various interpretations of the Invar effects, as well as the microscopic properties of the Invar alloys, are summarized. The physical background of the Elinvar alloys is also presented. Recent observations of Invar-type effects in new materials suggest that the Invar effect is rather common in itinerant ferro- and antiferromagnets. View full abstract»

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  • Magnetooptic properties and applications of bismuth substituted iron garnets

    Page(s): 292 - 311
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    Using the results of the phenomenological and microscopic description of magnetooptically active transitions presented in the beginning of the article, a review is made of the progress achieved in the understanding of the origin of the large bismuth induced magnetooptic effects in iron garnets. For applications involving the Faraday configuration, optical efficiencies are determined by the ratio of Faraday rotation (θ) to optical absorption (α). The dependence of θ/α on such variables as bismuth concentration,4piM_{s}and impurity ions is discussed with its spectral behavior. Finally, the behavior of bismuth substituted iron garnets in devices previously devised using unsubstituted iron garnets is discussed, in conjunction with devices which have only become feasible as a consequence of improvements in the optical properties of such iron garnets. View full abstract»

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  • Manganese bismuth and other magnetic materials for beam addressable memories

    Page(s): 311 - 327
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    Properties of materials which have highlighted research and development in the technology of beam accessible magnetic information storage are reviewed. Attention is focused on the advances made in understanding localized thermal magnetization reversal, bit stability and energy thresholds. View full abstract»

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  • Bubble domain memory materials

    Page(s): 327 - 345
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    The selection and preparation of bubble domain materials is discussed in the light of materials requirements for bubble domain memories. The history of bubble domain materials development is outlined with emphasis on the discovery and exploitation of two types of materials, magnetic garnets and amorphous magnetic alloys. It is shown how the great compositional flexibility of the garnet system has led to many garnet choices for device use without imposing undue hardship on the materials developer and supplier, and how liquid phase epitaxy of garnet films is a simple way of providing reproducibly films that meet device requirements. Amorphous magnetic alloys are discussed with emphasis on Gd-Co-Mo compositions. In the search for small bubble materials, it is pointed out that both garnets and amorphous alloys have limitations. In the former case,qwill usually be too low and in the latter case, the drift of properties with temperature may be unacceptable. View full abstract»

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  • On spontaneous nucleation in field-accessed bubble devices

    Page(s): 346 - 348
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    The dependence ot the in-plane drive field at which bubble domains spontaneously nucleate in field-accessed bubble devices has been investigated as a function ofH_{k} - 4piM_{s}and of spacer thickness between the bubble film and permalloy propagation elements. The experiments were carried out on amorphous GdCoMo bubble films with T-bar and Y-bar structures. For a given structure and spacer thickness the nucleation field increases linearly withH_{k} - 4piM. Larger spacer thicknesses also lead to increased nucleation fields. A model based on the Stoner-Wohlfarth astroid is compared to these data and found to be useful in explaining the qualitative trends, but to be in poor quantitative agreement. It is concluded that since the drive field required in a device is proportional to4piM_{s}, Q - 1 = (H_{k} - 4piM_{s})/4piM_{s}must be greater than some minimum value for a given device structure and spacer thickness to permit reliable device operation. View full abstract»

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  • Changes in recording tape magnetization produced by stress

    Page(s): 348 - 355
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    When mechanical forces are applied to single domain particles that are used in magnetic recording tapes, the resultant stress anisotropy energy alters the magnetized state, producing reversible and irreversible changes. We use four different experimental techniques to measure these changes and analyze the results in terms of the values for the saturation magnetostriction constants (λs) and the applied stress (σx). The reversible changes in magnetization (Mx) are roughly proportional tolambda_{s}sigma_{x}; the greatest irreversible or loss component occurs when the product of σxand λsalong the magnetizing axis (x) is negative, increasing when major easy axes make large angles withx. View full abstract»

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  • Magnetic recovery of sulphur from coal in Brasil

    Page(s): 355 - 358
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    Magnetic recovery of pyritic sulphur and coal from mine rejects has been envisaged as a two-step sequence of processes. 1) A thermal decomposition of the mixture rich in pyrites at about 700°C which produces a magnetic pyrrhotite and liberates sulphur; 2) air transport of the solid product into a high-gradient magnetic separator to separate coal from the minerals. Analysis is made of results reported separately on the kinetics of thermal decomposition of pyrites, carried out in thermo-balance, and on the wet slurry magnetic processing of coals. A suggestion is made to pursue sulphur recovery from coal mine rejects by using a proposed all-dry fluidized bed process, after the previous effort of other authors on dry magnetic processing of pyrites mentioned in the literature. This suggestion is the principal aim of this work. View full abstract»

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  • Characterization of magnetic forces by means of suspended particles in paramagnetic solutions

    Page(s): 359 - 368
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    A new technique, whereby the so-called "iso-directional-force lines" may be illustrated directly, is proposed. The method is based on the levitation forces acting on a particle immersed in paramagnetic fluid in nonhomogeneous magnetic field. An ordered set of capillaries, each containing a small particle suspended in the fluid, may be used to depict the iso-directional-force lines by the equilibrium positions of the particles. Once the field is mapped (by a selected standard system), its characteristics are known, with respect to any other fluid particle combinations. The latter is of significance for research and technology. View full abstract»

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  • An investigation of two HSGT magnetic suspension systems (attraction)

    Page(s): 369 - 372
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    Two alternate attraction magnetic suspension systems are discussed on a magnetic performance basis, as well as on their lift-to-weight (L/W) capabilities. On an equal current basis, the lower reluctance, flat track configuration has higher lift force and betterL/Wthan the U-shaped track configuration with its larger leakage flux. With equal magnetization (unequal currents) and low guidance forces (F_{G}/F_{L} leq 0.3), the U-shaped track has a higherL/Wratio, but both attraction systems suffer from lowL/Wwhen all elements of the suspension system are considered. View full abstract»

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  • Topological considerations of parametric electromechanical devices and their parametric analysis

    Page(s): 373 - 380
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    One of the methods for attaining free suspension of objects in magnetic fields is magnetic levitation by tuned circuits. Tuned-circuit levitators exhibit typical dynamic instability. However, the inherent tendency of the suspended object to oscillate may serve as a basis for the construction of relatively new types of machines. An attempt is made to treat, all these devices from a generalized point of view. A method similar to that used for the analysis of parametric electronic networks is suggested here to tackle parametric electromechanical systems. The paper concludes with two recent examples which illustrate how unexpected are the phenomena, where parametric electromechanical effects are of relevance. A peculiar mechanical instability which occurred in the VHF resonators used in particles accelerators, has been described recently. It has also been found that both a rotation of a suspended object as well as its levitation can be achieved by using a levitator with only one electromagnet. View full abstract»

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  • Multimodal operation of a ferroresonant circuit with quintic nonlinearity

    Page(s): 380 - 384
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    The multimodal operation (jump phenomenon) of a ferroresonant circuit of practical interest is analyzed using West's method of frequency-damping boundaries with a fifth-order approximation for the saturation curve of the nonlinear inductor. For given circuit parameters, the applied voltage range over which ferroresonance can occur is determined, and it is shown that this method gives more precise information than the incremental describing function method on the possibility that a certain applied voltage will produce the jump phenomenon. View full abstract»

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  • An accurate AC demagnetizing method using a linear inductance for high permeability cores

    Page(s): 385 - 389
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    A new simple and accurate ac demagnetizing method for high permeability cores is presented. In this method, a linear inductance is connected in parallel with the winding of the core to stabilize the level ofBHminor loops at zero flux level during the whole process of ac demagnetization. The ac demagnetization error is suppressed to less than 0.5% even in 50% Ni-Fe cores. The optimal ac demagnetizing time is longer than 0.5 sec., and the optimal ac demagnetizing waveform of current source is sinusoidal. Experimentally, high demagnetizing accuracy was obtained over a frequency range of 10 Hz-2 kHz. Two cores with the same dimensions and materials are simultaneously ac demagnetized by means of a linear inductance connected in parallel with the primary windings of two cores connected series-aiding, whose secondary windings are connected parallel-opposing and short circuited; thus, the remanent flux level after ac demagnetization is nondestructively detected by destructive readout in other core. This ac demagnetizing method is useful for measuring some magnetic properties such as initial permeability and BH curves and for resetting the small-signal transformer cores and second-harmonic analog memory elements. View full abstract»

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  • Transfilter

    Page(s): 389 - 392
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    The Transfilter is a combination of a leakage-reactance magnetic structure and a capacitor, which is interposed between an ac thyristor voltage controller and the load, to filter the load current, to provide current-source characteristics, and to act as an isolation and impedance-level transformer. The Transfilter was originally developed to provide sinewave adjustable current up to 50 A at 60 Hz for an automatic power-system-relay tester. View full abstract»

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  • A study of magnetic hardening in Pt1-xNixFe

    Page(s): 393 - 395
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    Alloys of composition Pt1-xNixFe withx = 0.2, 0.3, and 0.4 can be quenched from high temperature to retain a face centred cubic disordered phase. On aging, at lower temperatures, alloys withx = 0.2 and 0.3become magnetically hard with coercivities up to 2000 Oe at room temperature. In the hardened state the alloys have an ordered tetragonal structure withc/a sim 0.96and a uniaxial magnetocrystalline anisotropy ofsim10^{7}erg cm-3. Electron microscopy, of magnetically hard fully tetragonal samples, reveals a {110} lamellar structure. Thecaxis of each lamella is at 90° to thecaxis of the locally dominant tetragonal matrix phase in which it is embedded. Lorentz microscopy reveals domain walls, parallel to the dominantcaxis which are "kinked" where they cross lamellae. The coercive forces increase on cooling below room temperature. This increase can be attributed to the decreased probability of the thermal activation of domain wall segments, over barriers, as the temperature falls. An alloy withx = 0.4formed a cubic ordered phase on aging but did not develop high coercivity or high remanent magnetization. View full abstract»

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  • Deposition of magnetite films by reactive sputtering of iron

    Page(s): 396 - 400
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    Iron is sputtered reactively in an argon-oxygen glow discharge to form deposits of magnetite. Cycling the oxygen partial pressure between a low and a high value during sputtering causes deposition of alternating layers of Fe-metal and Fe2O3-oxide. Depending on the cycle length, a layered structure results or homogeneous films form. For all films pronounced magnetite peaks were found by X-ray analysis. In the case of homogeneous films only magnetite was found. The films were hard-magnetic with coercivities between 250 Oe and 550 Oe and squarenesses between 0.6 and 0.8. Magnetic recording of these films on 14-in disks yielded bit-densities of up to 6.5 kT/cm. View full abstract»

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  • Precession modes and resonance absorption in the canted antiferromagnet FeBO3

    Page(s): 401 - 404
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    Dynamic properties of the weak ferromagnet FeBO3were investigated. The dependence of resonance absorption χ" on the angle between the easy plane of magnetizations and the RF field is shown. The calculation of the frequency dependence of the resonant precession modes for the low- and high-frequency branch is presented. Experimental results for the low-frequency branch show good agreement with theory. View full abstract»

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  • Ferro-antiferromagnetic transition in the alloy system Fe65(Ni1-xCrx)35at low temperatures

    Page(s): 404 - 406
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    The magnetic and electric properties of iron-nickel "invar" alloys and stainless steels are measured at low temperatures. It is shown that "invar" alloys such as stainless steels exhibit one-directional anisotropy, and their electric and galvanomagnetic properties are rather specific. It is shown also that the concentration dependence of Neel temperatures and magnetoresistance for the systems Fe-Ni and Fe65(Ni1-xCrx)35are similar. View full abstract»

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  • High-frequency investigations of magnetic noise characteristics

    Page(s): 406 - 410
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    Allowing for the magnetic noise damping effect, characteristic changes in the noise spectrum between 1.5-100 kHz are investigated as a function of magnetizing frequency, and corresponding damping-corrected power spectra are outlined. A Systematic comparison is carried out between high-frequency noise characteristics and properties of a low-alloy steel sheet quality, the dependence found being more or less fortuitous. View full abstract»

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  • Block oriented bubble domain memory organization

    Page(s): 411 - 413
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    A block oriented bubble domain memory organization is proposed which provides a block access time improvement over existing major/minor loop designs and which exhibits built-in redundancy. Wafer level integration is utilized to reduce the module lead count. View full abstract»

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  • [Back cover]

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    Freely Available from IEEE
  • Magnetooptical investigation of the permalloy overlay at micron resolution

    Page(s): 413 - 415
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    The distribution of magnetizationMin T and I elements at various orientations and values of external magnetic fieldHwas investigated. It has been discovered that there is a strong mutual influence of adjacent bars on the distribution ofMin T- and I-bars. Direct observations of the magnetization distribution in the I-bar in the presence of bubble field were performed. 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.

Full Aims & Scope

Meet Our Editors

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