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Magnetics, IEEE Transactions on

Issue 11  Part 2 • Date Nov. 2009

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  • [Front cover]

    Publication Year: 2009 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2009 , Page(s): C2
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  • Table of contents

    Publication Year: 2009 , Page(s): 5177 - 5178
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  • The 7th International Symposium on Hysteresis Modeling and Micromagnetics Conference Co-Chairs' Foreword

    Publication Year: 2009 , Page(s): 5179
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  • Monte Carlo Simulation of the FM Layer Thickness Influence on the Exchange Bias in FM/AFM Bilayers

    Publication Year: 2009 , Page(s): 5180 - 5183
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    A Monte Carlo simulation study of the exchange bias properties in ferromagnetic/antiferromagnetic (FM/AFM) bilayers by using a classical Heisenberg model and the Metropolis algorithm is addressed. In our model several contributions including nearest neighbors exchange interactions, two different interface couplings, magnetocrystalline anisotropy, and a Zeeman term were considered. Our study focuses on the influence of FM and AFM layer thicknesses (dF and dA ) on hysteresis loops, particularly exchange bias field (HEB) and coercive force (Hc) . Results reveal that the influence of dA on the exchange bias phenomenon is negligible, while dF produces an important effect on HEB and Hc. Such behaviors agree with several models and results reported in the literature. Concretely, our model allows inferring a dependence of the exchange bias field with the FM layer thickness proportional to 1/(dF)m characterized by an exponent m = 0.71plusmn0.11. On the other hand, coercive force exhibits a power law increase with the FM layer thickness when thermal fluctuations become relevant. For completeness, thermal stability of the hysteretic properties is finally presented and discussed. View full abstract»

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  • Representation of Memory in Particle Assembly Hysteresis Models

    Publication Year: 2009 , Page(s): 5184 - 5187
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB) |  | HTML iconHTML  

    We have developed a mathematical tool able to track irreversible processes in magnetic systems described by the Stoner-Wohlfarth model, under any applied field history. A graphic representation is worked out that accounts for interactions, and turns out to be an extension of the one operating in the Preisach model. The response to alternating and rotating magnetizing fields have been investigated in detail. We have found a strategy in dealing with hysteretic memory effects which speeds the computational work needed to get the materials magnetization. This approach can represent a suitable tool aimed at estimate the energy loss and entropy production in magnetic systems. View full abstract»

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  • Measurement and Simulation of Vector Hysteresis Characteristics

    Publication Year: 2009 , Page(s): 5188 - 5191
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (441 KB) |  | HTML iconHTML  

    This paper presents a Preisach model of ferromagnetic hysteresis to simulate the vector hysteresis properties of ferromagnetic materials. Vector behavior has been studied using a single sheet tester with a round shaped specimen at low frequency, and the magnetic flux density vector has been controlled by a digital measurement system. Circular magnetic flux density pattern has been measured. An inverse vector Preisach hysteresis model has been developed and identified by applying the measured data. Finally, the inverse model has been inserted into a finite element procedure through the fixed point technique and the reduced magnetic scalar potential formulation. The applicability of the measurement system as well as the developed model has been proven by comparing measured and simulated results. View full abstract»

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  • Analysis of a Unit Magnetic Particle Via the DPC Model

    Publication Year: 2009 , Page(s): 5192 - 5195
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (166 KB) |  | HTML iconHTML  

    This paper presents a discussion of the properties and the behavior of an unit magnetic particle as calculated by the DPC (Della Torre, Pinzaglia and Cardelli) model. The general mathematical expressions of the vector field generated by the unit magnetic particle are derived in a special regular parametric coordinates system. It is shown that, in a special case, the DPC model leads to the same results as in the Stoner-Wohlfarth dealing with the physics of an ellipsoidal, single-domain, uniaxial magnetic particle. Some numerical examples for a possible use of the DPC model in the analysis of nanomagnetic samples are presented. View full abstract»

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  • Geometry Influence on the Hysteresis Loops Behavior in La _{2 / 3} Ca _{1 / 3} MnO _{3} Nanoparticles. Monte Carlo Simulation on a Heisenberg-Like Model

    Publication Year: 2009 , Page(s): 5196 - 5199
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB) |  | HTML iconHTML  

    In this study we emphasize on the role of the geometry upon the magnetic and critical properties of ferromagnetic manganite nanoparticles having stoichiometry La2/3Ca1/3MnO3. To do that, we consider a set of fine particles of different shapes (spherical and polyhedral) containing approximately the same amount of ions (~8000 magnetic Mn ions) and distributed according to a simple cubic structure. The method is based on the standard Monte Carlo-Metropolis technique. Our theoretical framework employs a classical Heisenberg-like Hamiltonian, where different magnetic nearest neighbor superexchange integrals, preserving orbital ordering for this composition, have been considered. Results showed the specific behavior of the Curie temperature and low temperature coercive force. The studies were done depending on the nanoparticle shapes. View full abstract»

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  • Multiscale Finite Element Solution of the Exchange Term in Micromagnetic Analysis of Large Bodies

    Publication Year: 2009 , Page(s): 5200 - 5203
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (851 KB) |  | HTML iconHTML  

    This paper presents a finite element formulation of the Landau-Lifschitz equation, where the exchange field is decomposed in a coarse-scale and a fine-scale term, following a multiscale approach. The proposed method is validated by comparison with a standard finite element solution considering some typical magnetization distributions in a thin film. Finally, a magnetization process in the same thin film is simulated and the results are found to be in satisfactory agreement with the standard finite element predictions. View full abstract»

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  • Critical Aspects in Micromagnetic Computation of Hysteresis Loops of Nanometer Particles

    Publication Year: 2009 , Page(s): 5204 - 5207
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    This paper discusses the criticalities occurring in the computation of hysteresis loops by the numerical space-time integration of the Landau-Lifshitz-Gilbert equation. The magnetization time-update is obtained by means of two norm-conserving algorithms, respectively based on midpoint rule and Cayley transform. The study gives hints for the definition of a correct criterion of convergence towards equilibrium states and for the improvement of the numerical efficiency, focusing on the reduction of the simulation duration. View full abstract»

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  • A Coupled Multipole Expansion—Finite Element Approach for Dynamic Micromagnetic Modeling

    Publication Year: 2009 , Page(s): 5208 - 5211
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    This paper presents a 3-D dynamic micromagnetic numerical procedure, which efficiently computes the magnetostatic field by approximating the contributions of far magnetic dipoles with a multipole expansion technique. This approach is coupled to a finite element spatial reconstructor of the effective field, which leads to the reduction of the second order derivative in the exchange term. The procedure is tested focusing on the influence of the multipole expansion approximation on numerical accuracy and efficiency. View full abstract»

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  • Thermally Initiated Reversal Modes in Infinite Periodic Ferromagnetic Wires

    Publication Year: 2009 , Page(s): 5212 - 5215
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    In finite ferromagnetic wires, the demagnetizing effects along the wire axis have a substantial influence on the reversal processes. By considering infinite wires, these effects are annihilated and only the sample dimensions, cross-sectional geometry, and material properties determine the magnetization reversal. The magnetization reversal is now initiated by small thermal fluctuations. With decreasing cross-sectional dimensions, three different reversal modes can be distinguished: reversal with (i) domain formation; (ii) vortex formation; and (iii) precessional switching combined with buckling. For different cross-sectional dimensions and lattice axes orientations, the 3-D magnetization dynamics and evolution of the different micromagnetic energy terms are investigated, resulting in a clear understanding of the reversal modes. View full abstract»

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  • Numerical Solutions of the Fokker–Planck Equation for Magnetic Nanoparticles

    Publication Year: 2009 , Page(s): 5216 - 5219
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    We present a method to solve numerically the Fokker-Planck equation for a uniformly magnetized nanoparticle. This approach is an algebraic formulation scheme that uses integral variables associated with space and time elements. This new method is compared with a spectral collocation method, similar to that referenced in a previous article. The stationary distribution, the eigenvalues of the Fokker-Planck operator, and the self-covariance function obtained from the two approaches are compared. The numerically calculated stationary distributions are also checked against analytical results. View full abstract»

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  • Numerical Analysis of the Nonlinear Excitation of Subcritical Spin-Wave Modes Within a Micromagnetic Framework

    Publication Year: 2009 , Page(s): 5220 - 5223
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (259 KB) |  | HTML iconHTML  

    A micromagnetic analysis of the excitation of subcritical bullet modes by spin-polarized currents in magnetic nanocontact systems is carried out by taking into account the contributions arising from Oersted and thermal fields. It is demonstrated that the former yields an increase of the value of the excitation thresholds, whereas the latter represents the source of the nonlinear fluctuations needed to excite such subcritical modes. View full abstract»

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  • Analytical Description of Quasi-Random Magnetization Relaxation to Equilibrium

    Publication Year: 2009 , Page(s): 5224 - 5227
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    The Landau-Lifshitz (LL) dynamics of a uniformly magnetized particle is considered. The LL equation is written in the form of a Hamiltonian perturbed dynamical system. By using suitable averaging technique, the equation for the slow dynamics of the energy is derived. The averaging technique breaks up in the case of separatrix crossing. It is shown that, in the limit of small damping, the separatrix crossing can be described by using a probabilistic approach. View full abstract»

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  • Hysteresis in Cognitive Processes

    Publication Year: 2009 , Page(s): 5228 - 5230
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB) |  | HTML iconHTML  

    Cognitive bias is a key feature of human decision making, and has an impact in a wide range of human endeavours. Certain features of the development of such bias suggest a hysteresis-type process at some level. Some possibilities for this process are suggested, and a simple model for the development of such bias introduced. Qualitative numerical results from this model are also presented. View full abstract»

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  • Modeling and Simulation of Noise Induced Phenomena in Complex Hysteretic Systems

    Publication Year: 2009 , Page(s): 5231 - 5234
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB) |  | HTML iconHTML  

    A unitary framework for the analysis of noise induced phenomena in complex hysteretic systems is developed and implemented in an open-access academic software. Various differential, integral, and algebraic models of hysteresis are considered while the input processes are generated from arbitrary given spectra. The statistical algorithm based on Monte-Carlo techniques and used to compute the stochastic characteristics of hysteretic systems is presented, along with several tests against analytical results available in the literature. This approach can be used to study various stochastic aspects of hysteresis, including thermal relaxation, data collapse, field cooling/zero field cooling, and noise passage. Several numerical simulations of noise induced phenomena in complex hysteretic systems are presented and their general qualitative features are discussed. View full abstract»

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  • Control-Oriented Hysteresis Models for Magnetic Electron Lenses

    Publication Year: 2009 , Page(s): 5235 - 5238
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (441 KB) |  | HTML iconHTML  

    This paper deals with finding appropriate hysteresis models that predict the behavior of electro-magnetic lenses used with electron microscopy. The iterative selection procedure consists of experiment design and mathematical analysis of hysteresis models. We will show two examples of pitfalls when the suitability of models is assessed by means of curve-fitting to observations. The first example illustrates the inability of models with local memory to describe the magnetic hysteresis in our application. The second deals with accommodation. With both, the experiments carried out on an off-line setup of a magnetic lens are compared to hysteresis models. View full abstract»

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  • Micromagnetic Analysis of Nonlinear Dynamics in Spintronic Analog Modulators

    Publication Year: 2009 , Page(s): 5239 - 5242
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    The simultaneous action of dc and ac spin-polarized current traversing a magnetic nanocontact device results in a combined amplitude-frequency nonlinear modulation process, a promising application of spin-transfer oscillators. A micromagnetic analysis of the nonlinear magnetization dynamics occurring in such devices is carried out in both spatial and frequency domain. Numerical results show that the proposed combined modulation scheme affects the amplitude of the sidebands as well as their phase, and remark a substantial difference with respect to the properties exhibited by a classical linear modulator. Further investigations performed as function of the frequency of the modulating signal allow to establish that, when the modulating frequency approaches the carrier one, no modulation occurs and a frequency pulling, typical of injection locking phenomena, takes place instead. View full abstract»

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  • Experimental Verification of the Deletion and Congruency Properties in Si-Fe Magnetic Steels

    Publication Year: 2009 , Page(s): 5243 - 5246
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    This work presents an experimental procedure to verify if a model of vector hysteresis, the DPC model (Della Torre, Pinzaglia, Cardelli), based on the Preisach theory, can be identified for a given material. The identification can be achieved only if the material has a magnetic behavior in agreement with the properties of congruency and deletion which characterize the model. Finally, we show some results obtained on a sample of commercial nonoriented magnetic steel. View full abstract»

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  • Theoretical Considerations of Magnetic Hysteresis and Transformer Inrush Current

    Publication Year: 2009 , Page(s): 5247 - 5250
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (145 KB) |  | HTML iconHTML  

    This paper presents an application of a hysteresis model that is coupled to an equivalent network for the calculation of the inrush current due to an arbitrary excitation of a transformer after a fault. The approach proposed, although using several simplifying assumptions, seems promising in order to calculate the optimal time to close the circuit after a fault. View full abstract»

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  • Ferromagnetic Nanoparticles Dose Based on Tumor Size in Magnetic Fluid Hyperthermia Cancer Therapy

    Publication Year: 2009 , Page(s): 5251 - 5254
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB) |  | HTML iconHTML  

    The interest in magnetic fluid hyperthermia (MFH) and cancer therapy has noticeably increased in the last years. At present, a successful realization of this interdisciplinary research is hampered by some unsolved problems. One of these problems this paper intended to clarify is how to find an estimate of the appropriate dosage of magnetic nanoparticles that injected into the tumor would help achieve an optimum temperature of 42degC, thus resulting in an increase of the susceptibility for apoptosis in tumor cells. We created a computational model in COMSOL: Multiphysics in order to analyze the heat dissipation within the tumor tissue. By considering various types of tissues with their respective physical and physiological properties (breast, liver, and skin tissues) and also by taking into account the amount of heat generated through the Brownian rotation and the Neel relaxation, it has been studied the tumor border temperature achieved for various concentrations of magnetic nanoparticles in their superparamagnetic behavior. Distinct simulations of a spherical tumor located in a cubical region of a volume of 1.2-3.5 cm3 within the tissue were designed. We performed a systematical variation of tumor diameter and particle dosage for every physical parameter of above mentioned tumor tissues (e.g., tissue density, tumor/tissue perfusion rate). By this systematization we intended to understand the interdependence of these parameters and their effects on hyperthermia therapy. View full abstract»

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  • Conference Author Index

    Publication Year: 2009 , Page(s): 5255
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  • Scitopia.org [advertisement]

    Publication Year: 2009 , Page(s): 5256
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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