By Topic

Magnetics, IEEE Transactions on

Issue 2  Part 1 • Date Feb. 2011

Filter Results

Displaying Results 1 - 25 of 26
  • [Front cover]

    Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (219 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Magnetics publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (39 KB)  
    Freely Available from IEEE
  • Table of contents

    Page(s): 269 - 270
    Save to Project icon | Request Permissions | PDF file iconPDF (69 KB)  
    Freely Available from IEEE
  • Chairman's Preface

    Page(s): 271
    Save to Project icon | Request Permissions | PDF file iconPDF (25 KB)  
    Freely Available from IEEE
  • The Magnetoelastic Ion: Friend and Foe to Microwaves

    Page(s): 272 - 278
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (926 KB) |  | HTML iconHTML  

    From the earliest years of ferrite development, spin-lattice interactions from select transition-metal (3dn) and rare-earth (4fn) ions have influenced key parameters of microwave device performance. Hysteresis loop squareness and coercivity, and magnetic loss that is related to the ferrimagnetic resonance linewidth will continue to depend on cautious inclusion of ions of the 3dn and 4fn series. As the promise of films and layers for planar devices are made more realizable by rapidly advancing deposition technologies, new challenges appear from the presence of stress imparted by mismatches at film/substrate interfaces. To offset unwanted effects of bias strains, increased use of magnetoelastic ions will become necessary. An additional feature made possible by deposition processing at temperatures lower than those of bulk ceramic sintering or melt-grown single crystals is the stabilization of cation valence states that do not normally occur in the thermodynamic equilibrium of conventional bulk ceramic processing. In the future that will undoubtedly involve structures of steadily decreasing dimensions, ferrite applications will have to account for surface compositional variations and interface stress effects. To this end, this article examines the physics that underlies the possible advantages and potential hazards to microwave technologies of the future, where magnetoelastic 3dn ions Mn3+, Fe4+, Fe2+, Co4+, Co2+, and Cu2+, as well as other ions such as Ho3+ or Dy3+ of the 4fn shell can influence the microwave performance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Nonlinear Landau-Lifshitz Equation: Ferromagnetic Resonance, Giant Magnetoimpedance, and Related Effects

    Page(s): 279 - 283
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (930 KB) |  | HTML iconHTML  

    We review recent work in which a methodology has been developed for solving the Landau-Lifshitz equation in its most general form, along with Maxwell's equations. The method has been applied to the solution of problems of giant magnetoimpedance and ferromagnetic resonance. Conditions for chaotic behavior have been explored. Perspectives for future applications are briefly discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Varactor and FMR-Tuned Wideband Band-Pass Filter Module With Versatile Frequency Tunability

    Page(s): 284 - 288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (743 KB) |  | HTML iconHTML  

    A varactor and FMR-tuned wideband band-pass filter (BPF) module with versatile frequency tunability has been devised and realized on RT/Duroid substrate. By connecting four variable capacitance diodes (varactors) to the four open-circuited stubs of an X-band passive composite-BPF and adjusting the reverse bias voltage from 2 to 22 V, the 3 dB passband of the passive composite-BPF was continuously tuned from 7.7-12.4 GHz to 11.4-17.5 GHz. The corresponding bandwidth (BW) was enlarged from 4.7 to 6.1 GHz and the upper frequency of the passband was extended from 12.4 to 17.5 GHz, namely, a total frequency span of 9.8 GHz. The BW of the passive composite-BPF was further FMR-tuned using a pair of Band-Stop Filter (BSF). By setting the reverse bias voltage at 22 V together with the bias magnetic fields at 3250 and 4200 Oe, respectively, to the two BSFs, the 6.1 GHz BW and 9.8 GHz frequency span were compressed to 1.4 GHz toward the high-end frequency. The 4.7 GHz BW and 9.8 GHz frequency span were also compressed to 1.0 GHz toward the low-end frequency with 2650 and 3500 Oe bias magnetic fields and 2 V reverse bias voltage. Thus, the combination of the varactor and FMR-tuning has facilitated versatile passband and its BW tuning covering the X-and Ku-bands with both large frequency tunability and greatly improved frequency selectivity. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sub-Terahertz Magnetic and Dielectric Excitations in Hexagonal Ferrites

    Page(s): 289 - 294
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (473 KB) |  | HTML iconHTML  

    Magnetic and dielectric resonances in the sub-terahertz (sub-THz) frequency range are observed in pure and Al-substituted hexagonal barium ferrite. A resonator based on magnetic excitations has been fabricated and its performance characteristics have been studied. The possible use of the resonator at sub-THz frequencies has been demonstrated. The resonator exhibited a loaded Q-factor of 150-330 in the frequency range 97-108 GHz. Dielectric resonances in a single-crystal barium hexaferrite are observed in the frequency range 75-110 GHz. The modes excited by circularly polarized electromagnetic waves show nonreciprocal propagation characteristics. The dielectric resonances may occur at a much higher frequency than ferromagnetic resonance. It is shown that degeneracy in the dielectric modes is lifted with an applied magnetic field H and that the modes can be tuned by 10 GHz or more with H. Data on frequencies of the modes versus H shows hysteresis. Theoretical predictions on H-tuning characteristics of the principal dielectric E11δ mode are in agreement with the data. The dielectric modes are of importance for the realization of low-loss devices, including resonators, isolators and phase shifters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave/Millimeter-Wave Garnet Films

    Page(s): 295 - 299
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB) |  | HTML iconHTML  

    A buffer liquid phase epitaxy method for lead free flux technology has been used to grow large size garnet single-crystal films. Lu2.1Bi0.9Fe5O12 (Bi:LuIG) films with excellent lattice match with the Gd3Ga5O15 (GGG) substrate and superior magnetic and magnetic-optical properties have been obtained by optimizing liquid phase epitaxy (LPE) technology. The saturation magnetization of the film is about 1562 Gs, the Faraday rotation is 1.6 ~ 2.0 deg/μm and the minimum ferromagnetic resonance (FMR) linewidth is 2ΔH = 5.1 Oe. Secondly, the growth of polycrystalline garnet films by radio-frequency (RF) magnetron sputtering has be introduced, and the effects of buffer layer, sputtering parameters and post annealing on the performance of Y3Fe5O12 (YIG) films have been investigated in details. It will be shown that garnet films with smooth surface and adjustable saturation magnetization can be obtained by using a SiO2 buffer layer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Estimation of Peak Frequency of Loss in Noise Suppressor Using Demagnetizing Factor

    Page(s): 300 - 303
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    This study analyzes the loss peak frequency of an integrated ferromagnetic noise suppressor by evaluating the demagnetizing field. An integrated ferromagnetic noise suppressor is fabricated using a regular silicon process, and relation between the loss peak frequency and demagnetizing field is evaluated. The demagnetizing factor is calculated by approximating the magnetic film by a slender ellipsoid. Measurements of a fabricated on-chip noise suppressor reveal that the loss is maximized at 7 GHz, which is equal to the calculated ferromagnetic resonance (FMR) frequency. Then, the relation between the loss peak frequency and FMR frequency are discussed with some magnetic films in our previous works. The loss peak frequencies in coplanar lines of various magnetic films with different ratios of the film thickness to the signal line width agree well with the FMR frequency of magnetic films. This result reveals that the shift of the loss peak depends on the demagnetizing field over a wide frequency range. Consequently, the loss peak frequency of the integrated ferromagnetic noise suppressor can be controlled as a function of demagnetizing field in the magnetic film. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Integrated Ferrite Film Inductor for Power System-on-Chip (PowerSoC) Smart Phone Applications

    Page(s): 304 - 307
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    An array of ferrite and air-core inductors was fabricated on silicon wafer to characterize inductor performance. The 1 μm and 2.5 μm thick ferrite films for the fabrication of inductors were prepared by dc magnetron sputtering. The inductance of the ferrite inductor increased with the thickness of ferrite film from 45.5 nH for 1 μm thick ferrite to 50 nH for 2.5 μm thick ferrite. The maximum Q-factor was obtained to be 59 at 2.87 MHz from 2.5 μm thick ferrite inductor, which is higher than 49.3 at 2.26 MHz for 1 μm thick ferrite inductor and 23.2 at 1.56 MHz for air-core inductor. Superimposed dc current of 1 μm and 2.5 μm thick ferrite inductors was estimated to be 2.5 A and 2.15 A, respectively, corresponding to a 5% drop in L at 10 MHz. In addition, the power efficiency of the buck dc-dc converter based on the studied ferrite inductors was calculated to be 91.7% for 2.5 μm thick ferrite inductor and 90.1% for 1 μm thick ferrite inductor at load current of 0.647 A. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave Complex Permeability and Permittivity Measurements of Commercially Available Nano-Ferrites

    Page(s): 308 - 312
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    The dielectric permittivity and magnetic permeability of nano-sized magnetic powders are studied for a wide microwave frequency range from 2 to 40 GHz. These powders are studied for their potential application as soft microwave absorbers in wireless systems as well as for use in the manufacture of small magnetic recording tape, transformers and circulators. A newly developed and precise transmission-reflection based waveguide technique has been used to carry out measurements across the eight frequency bands. These materials have been accurately characterized for the first time across this frequency range. In this paper, we present equations for simultaneous calculation of permittivity and permeability across a wide frequency band using the vector network analyzer. To account for variable sample thickness in the in-waveguide measurements, the algorithm for transmission and reflection calculations has been modified. The results show that the dielectric permittivity depends on the particle size and density of the sample used for measurement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spin-Wave Resonances Affected by Skin-Effect in Conducting Magnetic Nanowire Arrays at Terahertz Frequencies

    Page(s): 313 - 316
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (327 KB) |  | HTML iconHTML  

    The properties of localized standing spin wave (SW) resonances are investigated numerically for a regular 2-D array of 10 nm diameter, 300 nm long metallic (iron) nanowires, magnetized at different orientations of the bias magnetic field mmb H0 with respect to the wire axis. At 30 THz the penetration depth of the electromagnetic (EM) waves can be close to the diameter of the nanowires, leading to interesting resonance effects as a result of the inhomogeneous rf magnetization distribution across the nanowire diameter. The mathematical model considers the metallic character of the wires and the exchange interactions between the wires, when solving Maxwell equations simultaneously with the Landau-Lifshitz equation for the magnetization. The transmission coefficients |T21| of TEM waves through arrays with different wire radius were determined. There are well-defined extrema of |T21| at certain values of the bias magnetic field mmb H0, corresponding to ferromagnetic resonance (FMR) and antiresonance (FMAR) modes. The position of these maxima and minima does not depend on the orientation of H0, although |T21| is sensitive to the direction of mmb H0. The distribution of the rf magnetization component across the nanowire is calculated for the second and low order exchange SW modes. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Systematic Analysis and Engineering of Absorbing Materials Containing Magnetic Inclusions for EMC Applications

    Page(s): 317 - 323
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1222 KB) |  | HTML iconHTML  

    A methodology to efficiently design novel products based on magneto-dielectric materials containing ferrite or magnetic alloy inclusions is presented. The engineered materials should provide desirable frequency responses to satisfy requirements of electromagnetic compatibility/immunity over RF and microwave bands. The methodology uses an analytical model of a composite magneto-dielectric material with both frequency-dependent permittivity and permeability. The Bruggeman asymmetric rule for effective permeability of a composite is modified to take into account demagnetization factors of inclusions, and is shown to be applicable to platelet magnetic inclusions. Complex permittivity and permeability are extracted from the transmission-line measurements. A novel accurate and efficient curve-fitting procedure has been developed for approximating frequency dependencies of both permittivity and permeability of magneto-dielectric materials by series of Debye-like frequency terms, which is important for wideband full-wave numerical time-domain simulations. Results of numerical simulations for a few structures containing magneto-dielectric sheet materials and their experimental validation are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ab Initio Study on Manganese Doped Cadmium Ferrite (\hbox {Cd}_{1-x}\hbox {Mn}_{x}\hbox {Fe}_{2}\hbox {O}_{4})

    Page(s): 324 - 332
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1508 KB) |  | HTML iconHTML  

    Manganese doped cadmium ferrites (Cd1-xMnxFe2O4, x=0, 0.25, 0.5, 0.75, 1) were studied by using ab initio calculation based on generalized gradient approximation (GGA). The dependence of electronic structure and magnetic properties on the additional on-site Coulomb repulsion (U) was investigated. In the calculation, normal spinel structure is assumed. Exchange interactions between magnetic ions are calculated from the total energies of ferromagnetic and other spin configurations. The lattice constants given by GGA show a linear dependence on the concentration of Mn (x) . The local magnetic moments of Fe and Mn ions decrease as x increases. The exchange integral JAB is negative and its magnitude increase as x increases, while JBB1 shows a transition from antiferromagnetic to ferromagnetic value. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Millimeter-Wave Tunable Electromagnetic Absorber Based on \varepsilon -Al _{\rm x} Fe _{2-{\rm x}} O _{3} Nanomagnets

    Page(s): 333 - 336
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (401 KB) |  | HTML iconHTML  

    High-performance millimeter-wave absorber composed of ε-AlxFe2-xO3 nanomagnets is prepared by sol-gel techniques. Free space quasi-optical spectrometer equipped with a set of tunable backward-wave oscillators as power sources is used in this work to study the absorption property of this series of materials. Special aluminum-disc sample container with thickness of 2 mm is fabricated. Transmittance spectra of ε-AlxFe2-xO3 with different x values (x = 0.66 and 0.49) are recorded using our free space spectrometer. Strong magnetic absorption at 95 GHz (corresponding to x = 0.66) and 105 GHz (x = 0.49) are found. Combining the data obtained in this and previous work, second order polynomial curve is simulated to study the x parameter dependence of absorption frequencies. The simulation results are in good agreement with the experimental ones. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Substrate Temperature Dependent Anomalous Magnetic Behavior in \hbox {CoFe}_{2}\hbox {O}_{4} Thin Film

    Page(s): 337 - 340
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    Co-ferrite (CoFe2O4) thin films were pulsed laser deposited on fused quartz substrate at different substrate temperatures (TS) ranging from room temperature (RT) to 750°C in oxygen pressure of 0.16 mbar. All the deposited films were ex-situ annealed at different temperatures (TA) between 350 and 1100°C in air for 2 h and were furnace cooled. The spontaneous magnetization (4πMS) of the as deposited film shows an expected increase as TS goes up, but always remains smaller than the bulk target value. For the annealed films deposited at different TS, we observed that 4πMS of the films deposited at lower TS increases at a faster rate with the increase in TA than the films deposited at higher TS. The 4πMS values higher than the Co-ferrite bulk value (5300G) were observed in the annealed films deposited at lower TS . The highest value of 6550G has been observed for the RT deposited film annealed at 1000°C, which is 24% higher than the bulk value. These results are explained on the basis of grain growth and the cation distribution in the films. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interactions of Electromagnetic Waves With 3-D Opal-Based Magnetophotonic Crystals at Microwave Frequencies

    Page(s): 341 - 344
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (582 KB) |  | HTML iconHTML  

    The propagation of electromagnetic waves at microwave frequencies was investigated numerically in SiO2 opal based magnetic nanostructures, using rigorous mathematical models solving Maxwell's equations with electrodynamic boundary conditions, complemented by the Landau-Lifshitz equation. The numerical approach is based on the Galerkin's projection method using the decomposition algorithm on autonomous blocks with Floquet channels. The opal structure consists of 250 nm SiO2 nanospheres, with inter-sphere voids infiltrated with octagonal nanoparticles of either Ni0.7Zn0.3Fe2O4 with 4πMs=5 kG, or NiFe2O4 with 4πMs=3.12 kG . Both the opal matrix and the ferrite are assumed to be lossy through complex dielectric constants. The field dependence of the complex wave number of the fundamental extraordinary mode of the propagating EMWs in the 3-D opal-based magnetophotonic crystals was determined for transverse orientation of the bias magnetic field at a frequency of 9.375 GHz. The numerical technique shows an excellent agreement when applied to model recent experimental data of waveguide measurements on similar ferrite opals. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Narrow Ferromagnetic Resonance Linewidth Polycrystalline Zn-Ferrite Thin Films

    Page(s): 345 - 348
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (331 KB) |  | HTML iconHTML  

    Ferromagnetic resonance at 9.5 GHz was performed on ferrimagnetic nano-crystalline Zn-ferrite thin films deposited under different preparation conditions. A very low line width of 40 Oe was observed in as-sputtered 100 W thin films in perpendicular configuration. The pulsed laser deposited films show comparatively higher line widths. This work shows that it is possible to deposit ferrite thin films with low line width and good magnetization values without going through a high temperature processing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Micromagnetic Simulations of Vortex Resonances in Coupled Nanodisks

    Page(s): 349 - 354
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (657 KB) |  | HTML iconHTML  

    The high-frequency response of two magnetostatically coupled nanodisks supporting a vortex state within a stack has been investigated by means of 3-D dynamic micromagnetic simulations performed in the frequency domain. These spectra reveal one or two resonance lines according to the vortex polarizations and chiralities. These sub-gigahertz resonance modes are associated with vortex core modes. The magnetostatic coupling controlled by the interdisk distance affects both the structure of the vortex core modes and their associated resonance frequencies. In the regime of strong magnetostatic interaction, coupled vortex core modes are analyzed in terms of the relative phase relation between the vortex core motions. Lastly, the characteristics of the dynamic susceptibility spectra are also strongly dependent on the relative disk thicknesses. It results that these dynamic magnetic couplings play a major role in the high-frequency response of layered magnetic nanostructures and should be taken into account in the design of new spintronic or microwave devices based on vortex dynamics. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influences of Switching Field Rise Time on Microwave-Assisted Magnetization Reversal

    Page(s): 355 - 358
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    We present micro-magnetic simulations of the effects of switching field rise time on magnetization reversal for both exchange spring media (ESM) and single phase media (SPM). Numerical results yield the following. 1) As the rise time of switching field pulse decreases in a specific range, the coercivities of both medium for ESM and SPM drop significantly. This phenomenon is more obvious when the microwave frequency deviates from optimal frequencies where coercivities drops to a minimum. 2) The optimal frequency of ESM is lower than that of SPM. It becomes even lower as the rise time decreases. 3) With rise time ranging, oscillation of optimal frequency of ESM is lower than that of SPM. It decreases further as the rise time decreases. 4) For different rise times, oscillations of optimal frequencies coercivities occur in the simulations. This phenomenon is more obvious for SPM than that for ESM. We also observe that for larger damping constants in the ESM model, the optimal frequency coercivity fluctuations decrease gradually. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On-Chip Detection of Magnetic Dynamics for Single Microscopic Magnetic Dot

    Page(s): 359 - 361
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (311 KB) |  | HTML iconHTML  

    An inductive-based detection method of ferromagnetic resonance spectrum is demonstrated. For a single microscopic (~40 nm × 40 μm × 60 μm) magnetic dot, which is much smaller than the microwave wavelength, the change in the microwave transmission signal is as large as 15 dB when its magnetic permeability changes. This detection is several orders more sensitive than the conventional transmission line method. Further understanding and development of this concept may lead to a microscopic microwave permeability sensor. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Conference Author Index

    Page(s): 362
    Save to Project icon | Request Permissions | PDF file iconPDF (18 KB)  
    Freely Available from IEEE
  • 2011 IEEE membership form

    Page(s): 363 - 364
    Save to Project icon | Request Permissions | PDF file iconPDF (1362 KB)  
    Freely Available from IEEE
  • IEEE Magnetics Society Information

    Page(s): C3
    Save to Project icon | Request Permissions | PDF file iconPDF (31 KB)  
    Freely Available from IEEE

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