| 1. |
- Abeywickrama, K. G. Nilanga B., et al.
(author)
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Determination of complex permeability of silicon steel for use in high-frequency modeling of power transformers
- 2008
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In: IEEE transactions on magnetics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9464 .- 1941-0069. ; 44:4, s. 438-444
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Journal article (peer-reviewed)abstract
- Information about frequency dependence of complex permeability of silicon steel is a vital input parameter in calculations of transformer winding inductance used for modeling. high-frequency behavior (100 Hz-1 MHz). We present two ways of determining small signal complex permeability spectra in frequency domain and compare and discuss the results. The first method is based on an optimization procedure, in which inductance of a winding is measured and calculated by analytical formulas and finite-element modeling. The second method makes use of a single sheet tester. We show that the magnitude of effective permeability of the silicon steel laminations remains significant up to about 100 kHz. We also report on the effect of magnetic viscosity on complex permeability.
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| 2. |
- Abeywickrama, Nilanga, 1976, et al.
(author)
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Computation of Parameters of Power Transformer Windings for Use in Frequency Response Analysis
- 2007
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In: IEEE Transactions on Magnetics. - 0018-9464. ; 43:5, s. 1983-1990
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Journal article (peer-reviewed)abstract
- We present a 3-D model for calculating magnetic fields in a power transformer and the effective parameters (inductance and resistance)of its windings. The transformer is representative of large transformers with power ratings ranging from hundreds of kilovolt amperes to hundreds of megavolt amperes. The model accounts for anisotropic frequency-dependent properties of the laminated transformercore and eddy currents in the steel sheets. We discuss the results of the calculations performed in the frequency range 10 Hz–10 MHz, and show that the largest variations of both the magnetic field and parameters of the windings take place at frequencies below 10 kHz and, at frequencies higher than 1 MHz, the magnetic core does not significantly affect the variation of the effective parameters.
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| 3. |
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| 4. |
- Abrahamsson, Johan, 1977-, et al.
(author)
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A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
- 2014
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:9
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Journal article (peer-reviewed)abstract
- Brushless dc coreless electric machines with double-rotor and single-stator configuration have very low losses, since the return path of the magnetic flux rotates with the permanent magnets. The eddy-current loss in the stator is additionally very small due to the lack of iron, making it ideal for kinetic energy storage. This paper presents a design for self-bearing rotor suspension, achieved by placing the stator windings skewed on a conical surface. A mathematical analysis of the force from a skewed winding confined to the surface of a cone was found. The parametric analytical expressions of the magnitude and direction of force and torque were verified by finite-element method simulations for one specific geometry. A dynamic model using proportional-integral-differential control was implemented in MATLAB/Simulink, and the currents needed for the self-bearing effect were found by solving an underdetermined system of linear equations. External forces, calculated from acceleration measurements from a bus in urban traffic, were added to simulate the dynamic environment of an electrical vehicle.
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| 5. |
- Albertsson, Dagur Ingi, 1993-, et al.
(author)
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Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators
- 2019
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In: IEEE transactions on magnetics. - : IEEE Press. - 0018-9464 .- 1941-0069. ; 55:10
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Journal article (peer-reviewed)abstract
- Emerging spin-torque nano oscillators (STNOs) and spin-Hall nano oscillators (SHNOs) are potential candidates for microwave applications. Recent advances in three-terminal magnetic tunnel junction (MTJ)-based SHNOs opened the possibility to develop more reliable and well-controlled oscillators, thanks to individual spin Hall-driven precession excitation and read-out paths. To develop hybrid systems by integrating three-terminal SHNOs and CMOS circuits, an electrical model able to capture the analog characteristics of three-terminal SHNOs is needed. This model needs to be compatible with current electric design automation (EDA) tools. This work presents a comprehensive macrospin-based model of three-terminal SHNOs able to describe the dc operating point, frequency modulation, phase noise, and output power. Moreover, the effect of voltage-controlled magnetic anisotropy (VCMA) is included. The model shows good agreement with experimental measurements and could be used in developing hybrid three-terminal SHNO/CMOS systems.
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| 6. |
- Albertsson, D. I., et al.
(author)
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Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators
- 2019
-
In: Ieee Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 55:10
-
Journal article (peer-reviewed)abstract
- Emerging spin-torque nano oscillators (STNOs) and spin-Hall nano oscillators (SHNOs) are potential candidates for microwave applications. Recent advances in three-terminal magnetic tunnel junction (MTJ)-based SHNOs opened the possibility to develop more reliable and well-controlled oscillators, thanks to individual spin Hall-driven precession excitation and read-out paths. To develop hybrid systems by integrating three-terminal SHNOs and CMOS circuits, an electrical model able to capture the analog characteristics of three-terminal SHNOs is needed. This model needs to be compatible with current electric design automation (EDA) tools. This work presents a comprehensive macrospin-based model of three-terminal SHNOs able to describe the dc operating point, frequency modulation, phase noise, and output power. Moreover, the effect of voltage-controlled magnetic anisotropy (VCMA) is included. The model shows good agreement with experimental measurements and could be used in developing hybrid three-terminal SHNO/CMOS systems.
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| 7. |
- Andersson, Sebastian, et al.
(author)
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Thermoelectrically Controlled Spin-Switch
- 2010
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2140-2143
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Journal article (peer-reviewed)abstract
- The search for novel spintronic devices brings about new ways to control switching in magnetic thin-films. In this work we experimentally demonstrate a device based on thermoelectrically controlled exchange coupling. The read out signal from a giant magnetoresistance element is controlled by exchange coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is shown to vary strongly with changes in temperature, and both internal Joule heating and external heating is used to demonstrate magnetic switching. The device shows no degradation upon thermal cycling. Ways to further optimize the device performance are discussed. Our experimental results show a new way to thermoelectrically control magnetic switching in multilayers.
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| 8. |
- Anisimov, AN, et al.
(author)
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Magnetic anisotropies of Fe-n/V-m(001) superlattices determined by Ferromagnetic Resonance
- 1998
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In: IEEE TRANSACTIONS ON MAGNETICS. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0018-9464. ; 34:4, s. 873-875
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Journal article (other academic/artistic)abstract
- The temperature-dependent magnetic anisotropies of Fe-n/V-m(001) superlattices on MgO(001) were determined by Ferromagnetic Resonance (FMR). The re-layer thickness n ranges between 2 and 4 atomic layers. The shape anisotropy dominates, and the easy-axis o
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| 9. |
- Benbouzid, M. E. H., et al.
(author)
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Dynamic modelling of giant magnetostriction in Terfenol-D rods by the finite element method
- 1995
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In: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 31, s. 1821-1824
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Journal article (peer-reviewed)abstract
- As a contribution to the development of methods for the design and the analysis of devices based on giant magnetostrictive materials, a model for the simulation of the dynamic behaviour of the nonlinear magnetoelastic medium is presented. The coupled magnetic, magnetoelastic and mechanical equations that describe the magnetostrictive problem are solved by means of the finite element method. The thin sheets bending principle (surface splines) is used to introduce in the simulation the nonlinear properties of giant magnetostrictive materials, obtained by static characterizations
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| 10. |
- Bergqvist, A., et al.
(author)
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A stress-dependent magnetic Preisach hysteresis model
- 1991
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In: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 27, s. 4796-4798
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Journal article (peer-reviewed)abstract
- The authors present a generalization of the classical Preisach model which handles coupled magnetic and mechanical hysteresis. Magnetostrictive materials are known to have hysteresis with respect to both magnetic field H and mechanical stress lambda;. To test the validity of the model, experiments where the two components H and lambda; have been verified in many different ways have been performed on Terfenol-D and compared to results computed from the model. Some of these results are presented. This stress-dependent model is found to have an accuracy comparable to that of the classical Preisach model
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| 11. |
- Bergqvist, A., et al.
(author)
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A thermodynamic representation of pseudoparticles with hysteresis
- 1995
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In: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 31, s. 3539-3541
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Journal article (peer-reviewed)abstract
- A method of expressing pseudoparticles with hysteresis within a context of irreversible thermodynamics is investigated. The state of a pseudoparticle is uniquely determined by its magnetization and its evolution is governed by entropy maximization. Hysteresis appears if the free energy is a nonconvex function of magnetization. The vectorial nature of magnetization and dependence on rate are accounted for in a systematic manner. Some basic properties are derived for quasistatic processes. In particular, it is found that in the scalar case, the magnetization is a monotonically increasing functional with respect to field and that for quasistatic processes, this implies the wiping-out property
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| 12. |
- Bergqvist, A. J., et al.
(author)
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A homogenization procedure of field quantities in laminated electric steel
- 2001
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In: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 37:5, s. 3329-3331
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Journal article (peer-reviewed)abstract
- A method for representing structures of laminated electric steel is investigated. The average behavior of laminates, including eddy current effects, is approximately represented using a rate-dependent constitutive law. The accuracy of the method is studied by comparing the homogenized description with finite difference calculations.
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| 13. |
- Bissal, Ara, 1986-, et al.
(author)
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Comparison of two Ultra-fast actuator concepts
- 2012
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In: IEEE transactions on magnetics. - : IEEE Press. - 0018-9464 .- 1941-0069. ; 48:11, s. 3315-3318
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Journal article (peer-reviewed)abstract
- In this paper, two different types of ultra-fast electromechanical actuators are compared using a multi-physical finite element simulation model that has been experimentally validated. They are equipped with a single-sided Thomson coil (TC) and a double-sided drive coil (DSC), respectively. The former consists of a spirally-wound flat coil with a copper armature on top, while the latter consists of two mirrored spiral coils that are connected in series. Initially, the geometry and construction of each of the actuating schemes are discussed. Subsequently, the theory behind the two force generation principles are described. Furthermore, the current, magnetic flux densities, accelerations, and induced stresses are analyzed. Moreover, mechanical loadability simulations are performed to study the impact on the requirements of the charging unit, the sensitivity of the parameters, and evaluate the degree of influence on the performance of both drives. Finally, it is confirmed that although the DSC is mechanically more complex, it has a greater efficiency than that of the TC.
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| 14. |
- Bissal, Ara, et al.
(author)
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On the Design of a Linear Composite Magnetic Damper
- 2015
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In: IEEE transactions on magnetics. - : IEEE Press. - 0018-9464 .- 1941-0069. ; 51:11
-
Journal article (peer-reviewed)abstract
- High-voltage direct current (HVdc) breakers are the key components in the realization of multiterminal HVdc grids. In the presence of fault current, these breakers should be able to deliver impulsive forces to swiftly open the metallic contacts. After the acceleration phase, the moving armature should be decelerated using controllable forces to avoid plastically deforming fragile components integrated in the system. In this paper, finite-element method-based simulation models, complimented with small-scale and large-scale experimental prototypes, were utilized to benchmark different damping topologies. It was found that a Halbach-based configuration can deliver a damping force that is almost two and a half times larger than its sequel. Its sequel, composed of vertically stacked oppositely oriented magnets, is easier to assemble and is also capable of generating a considerable damping force. Finally, it has been shown that both these schemes, inserted in a composite tube, have a potential to be used as dampers in HVdc breakers.
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| 15. |
- Bjurman, U., et al.
(author)
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Separation of high and low frequency behavior in non-linear circuit simulation, excited with modulated signals
- 2000
-
In: IEEE transactions on magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 36:4, s. 968-970
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Journal article (peer-reviewed)abstract
- Exciting nonlinear circuits with modulated signals will generate crossmodulation frequencies. In ordinary simulation techniques this makes time stepping methods a necessity, In the case of EMC-testing where the carrier frequency is as high as 2 GHz and the modulating frequency only 1 kHz, the simulation time will be extremely long. This paper presents Time Domain Frequency Separation (TDFS), a method,where the high and low frequency behavior is calculated separately to decrease the computation time. In a simulation made with Saber the calculation took approximately fourteen hours, and with TDFS in Matlab two minutes.
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| 16. |
- Bormann, Dierk, et al.
(author)
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Reluctance Network Method for Calculating the Series Impedance Matrix of Multi-Conductor Transmission Lines
- 2013
-
In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 49:10, s. 5270-5279
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Journal article (peer-reviewed)abstract
- The theoretical foundation of a recently proposed reluctance network method for computing the complex series impedance matrix of multi-conductor transmission lines is presented in detail, and the method is extended to more general cross section geometries with gaps of non-constant width between the conductors. It is argued that the method becomes exact in the limit of high frequencies and narrow gaps between the conductors. This limit usually is the most difficult one in alternative approaches, especially when the proximity effect is concerned. The method is verified by comparison with the exact solution of a stacked-slabs geometry, and with finite-element field calculations on a geometry consisting of tightly packed, round wires, surrounded by a shield.
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| 17. |
- Bormann, Dierk, et al.
(author)
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Reluctance Network Treatment of Skin and Proximity Effects in Multi-Conductor Transmission Lines
- 2012
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 48:2, s. 735-738
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Journal article (peer-reviewed)abstract
- A novel method is developed to easily compute the complex series impedance matrix of amulti-conductor transmissionline in a wide frequency range. It is based on a network of complex reluctances describing flux paths around the conductors. The network parameters are derived from the geometry of the conductor-insulator arrangement and from its material parameters. The method is best suited for situations where the typical gap width between conductors is much smaller than their thicknesses, where it provides an accurate treatment of both skin and proximity effects. Especially the proximity effect is hard to treat by other means in that limit. The method is demonstrated for an idealized example geometry, where its accuracy is verified with harmonic FEM field calculations.
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| 18. |
- Burgos Parra, Erick Omar, et al.
(author)
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Holographic imaging of magnetization in a single layer nano-contact spin transfer oscillator
- 2016
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In: IEEE transactions on magnetics. - 0018-9464. ; 52:7
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Journal article (peer-reviewed)abstract
- Time-averaged images of the magnetization within single layer spin transfer oscillators have been obtained using the holography with extended reference by autocorrelation linear differential operator (HERALDO) technique. Transport measurements on a Pd(5)-Cu(20)-Ni81Fe19(7)-Cu(2)-Pd(2) (in nm) stack with a 100 nm diameter nano-contact reveal the presence of vortex dynamics. Magnetic images of the device for injected current values of 24mA and -24mA suggest that a vortex has been ejected from the nano-contact and become pinned at the edge of the region that is visible through the Au mask.
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| 19. |
- Cherepov, Sergiy, et al.
(author)
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Micromagnetics of Spin-Flop Bilayers : S, C, and Vortex Spin States
- 2010
-
In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2124-2127
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Journal article (peer-reviewed)abstract
- Spin-flop tunnel junctions subjected to strong gigahertz excitations are found to exhibit highly stable resistance states, intermediate between the two spin-uniform ground states of high and low resistance. The associated spin distributions are necessarily nonuniform and differ significantly from the ground-state anti-parallel spin configuration in their static and dynamic properties. Detailed micromagnetic modeling reveals that inplane spin vortices in dipole-coupled thin-film bilayers are stable spin configurations, where the orientation of the vortex cores and the vortex chirality play an important role in the response of the system to external magnetic fields.
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| 20. |
- Cherepov, Sergiy, 1981-, et al.
(author)
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Resonant Switching of Two Dipole-Coupled Nanomagnets
- 2010
-
In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2112-2115
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Journal article (peer-reviewed)abstract
- The storage layer of recently developed spin-flop magnetic random-access memory consists of two closely spaced dipole-coupled nanomagnets and is highly stable in the ground state as well as in quasistatic fields applied off the easy axis. We show experimentally and confirm by using micromagnetic simulations that these spin-flop bilayers can be switched relatively easily by dynamic fields, applied at the frequency of the optical spin resonance of the bilayer. The field amplitude sufficient for this resonant switching can be an order of magnitude lower than the fields necessary for quasistatic reversal. Our data and micromagnetic analysis suggest that thermal agitation can play a role in the observed resonant switching behavior.
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| 21. |
- Chumak, A. V., et al.
(author)
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Advances in Magnetics Roadmap on Spin-Wave Computing
- 2022
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In: IEEE Transactions on Magnetics. - 0018-9464. ; 58:6
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Journal article (peer-reviewed)abstract
- Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction. Author
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| 22. |
- Danielsson, Oskar, et al.
(author)
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Flux Distribution in Linear Permanent-Magnet Synchronous Machines Including Longitudinal End Effects
- 2007
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 43:7, s. 3197-3201
-
Journal article (peer-reviewed)abstract
- We investigated the longitudinal ends' influence on the flux distribution in a permanent-magnet linear synchronous machine with an analytic model and with numeric finite-element methods. We derived a general analytic expression, on closed form, from a linear reluctance model. The model reveals that the flux in a linear machine differs from that in a rotating machine in several aspects. The longitudinal ends introduce a pairwise coupled flux pattern, which will behave differently in circuits with odd or even numbers of magnets. In linear machines with an even number of magnets the pairwise coupled flux will spread throughout the whole machine, whereas in linear machines with an odd number of magnets it will be transformed into an equally distributed flux in the middle. The latter case will give rise to a nonsymmetric air gap flux distribution, where every second pole has larger flux. We confirmed the pairwise coupled flux and the nonsymmetric air gap distribution predicted by the analytic model by finite-element simulations. We noted additional effects when nonlinear behavior of the steel is taken into account. We conclude that saturation counteracts the pairwise coupled flux pattern at the longitudinal ends. Again, a nonsymmetric air gap flux distribution occurs as the pairwise coupled flux is transformed into an equally coupled flux. The pairwise coupling of the flux and the nonsymmetric air gap flux distribution give rise to a number of secondary effects, which we discuss.
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| 23. |
- Dave, Renu W., et al.
(author)
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MgO-based tunnel junction material for high-speed toggle magnetic random access memory
- 2006
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 42:8, s. 1935-1939
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Journal article (peer-reviewed)abstract
- We report the first demonstration of a magnetoresistive random access memory (MRAM) circuit incorporating MgO-based magnetic tunnel junction (MTJ) material for higher performance. We compare our results to those of AlOx-based devices, and we discuss the MTJ process optimization and material changes that made the demonstration possible. We present data on key MTJ material attributes for different oxidation processes and free-layer alloys, including resistance distributions, bias dependence, free-layer magnetic properties, interlayer coupling, breakdown voltage, and thermal endurance. A tunneling magnetoresistance (TMR) greater than 230% was achieved with CoFeB free layers and greater than 85% with NiFe free layers. Although the TMR with NiFe is at the low end of our MgO comparison, even this MTJ material enables faster access times, since its TMR is almost double that of a similar structure with an AlOx barrier. Bit-to-bit resistance distributions are somewhat wider for MgO barriers, with sigma about 1.5% compared to about 0.9% for AlOx. The read access time of our 4 Mb toggle MRAM circuit was reduced from 21 ns with AlOx to a circuit-limited 17 ns with MgO.
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| 24. |
- Dumas, Randy K., et al.
(author)
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Graded Anisotropy FePtCu Films
- 2011
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 47:6, s. 1580-1586
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Journal article (peer-reviewed)abstract
- The fabrication and subsequent analysis of continuously graded anisotropy films are discussed. During deposition, a compositional gradient is first achieved by varying the Cu concentration from Cu-rich (Fe53Pt47)(70)Cu-30 to Cu-free Fe53Pt47. The anisotropy gradient is then realized after thermal post-annealing, and by utilizing the strong composition dependence of the low-anisotropy (A1) to high-anisotropy (L1(0)) ordering temperature. The magnetic properties are investigated by surface sensitive magneto-optical Kerr effect and alternating gradient magnetometer (AGM) measurements. AGM first-order reversal curve (FORC) measurements are employed in order to provide a detailed analysis of the reversal mechanisms, and therefore the induced anisotropy gradient. At low annealing temperatures, the FORC measurements clearly indicate the highly coupled reversal of soft and hard phases. However, significant interdiffusion results in virtually uniform films at elevated annealing temperatures. Additionally, the A1 to L1(0) ordering process is found to depend on the film thickness.
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| 25. |
- Dumas, Randy K., et al.
(author)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:6, s. 4100107-
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Journal article (peer-reviewed)abstract
- We present a comprehensive review of the most recent advances in nanocontact spin torque oscillators (NC-STOs). NC-STOs are highly tunable, with both applied magnetic field and dc, broadband microwave signal generators. As opposed to the nanopillar geometry, where the lateral cross section of the entire device has been confined to a typically <100 nm diameter, in NC-STOs, it is only the current injection site that has been laterally confined on top of an extended magnetic film stack. Three distinct material combinations will be discussed: 1) a Co/Cu/NiFe pseudospin valve (PSV) where both the Co and NiFe have a dominant in-plane anisotropy; 2) a Co/Cu/[Co/Ni](4) orthogonal PSV where the Co/Ni multilayer has a strong perpendicular anisotropy; and 3) a single NiFe layer with asymmetric non-magnetic Cu leads. We explore the rich and diverse magnetodynamic modes that can be generated in these three distinct sample geometries.
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