Showing papers in "IEEE Transactions on Magnetics in 2011"
TL;DR: In this article, the principles of operation of permanent magnets are summarized, and their development is reviewed, together with the limits of 1/4 μ0/Ms2 on energy product and 2K1/μ0Ms on coercivity, where K1 is the uniaxial anisotropy constant and Ms is the spontaneous magnetization.
Abstract: The principles of operation of permanent magnets are summarized, and their development is reviewed. The key figure of merit, the energy product, improved exponentially over much of the 20th century, doubling roughly every 12 years. Yet it has not improved significantly in the last 20 years. Constraints on further development are explained, together with the limits of 1/4 μ0/Ms2 on energy product and 2K1/μ0Ms on coercivity, where K1 is the uniaxial anisotropy constant and Ms is the spontaneous magnetization. The challenge of making rare-earth free magnets with a large energy product is discussed, as well as nanocomposite megajoule magnets and the development of new magnetically hard thin-films with perpendicular anisotropy which are potentially interesting for spin electronics or magnetic recording.
448 citations
TL;DR: In this paper, the effects of coil misalignment and geometry are addressed in a single mathematical expression for inductively coupled wireless power transfer, and a novel analytical power transfer efficiency model is presented.
Abstract: A novel analytical model of inductively coupled wireless power transfer is presented. For the first time, the effects of coil misalignment and geometry are addressed in a single mathematical expression. In the applications envisaged, such as radio frequency identification (RFID) and biomedical implants, the receiving coil is normally significantly smaller than the transmitting coil. Formulas are derived for the magnetic field at the receiving coil when it is laterally and angularly misaligned from the transmitting coil. Incorporating this magnetic field solution with an equivalent circuit for the inductive link allows us to introduce a power transfer formula that combines coil characteristics and misalignment factors. The coil geometries considered are spiral and short solenoid structures which are currently popular in the RFID and biomedical domains. The novel analytical power transfer efficiency expressions introduced in this study allow the optimization of coil geometry for maximum power transfer and misalignment tolerance. The experimental results show close correlation with the theoretical predictions. This analytic technique can be widely applied to inductive wireless power transfer links without the limitations imposed by numerical methods.
355 citations
TL;DR: In this article, an analytical subdomain model is presented to compute the magnetic field distribution in surface-mounted permanent magnet motors with semi-closed slots, which accurately accounts for armature reaction magnetic field and mutual influence between the slots.
Abstract: This paper presents an analytical subdomain model to compute the magnetic field distribution in surface-mounted permanent-magnet (PM) motors with semi-closed slots. The proposed model is sufficiently general to be used with any pole and slot combinations including fractional slot machines with distributed or concentrated windings. The model accurately accounts for armature reaction magnetic field and mutual influence between the slots. The analytical method is based on the resolution of two-dimensional Laplace's and Poisson's equations in polar coordinates (by the separation of variables technique) for each subdomain, i.e., magnet, air gap, slot-opening, and slots. Magnetic field distributions, back-EMF, and electromagnetic torque (including cogging torque) computed with the proposed analytical method are compared with those issued from finite-element analyses.
218 citations
TL;DR: A 6-slot-8-pole hybrid excitation flux switching machine, in which both permanent magnets and wound field excitation are employed as magnetomotive force sources is designed and demonstrated that the machine designed becomes a good candidate for the target HEV drive application.
Abstract: Over the last decade, many automotive companies have been commercializing hybrid electric vehicles (HEVs) as one of candidates for sustainable human life. Some of the recent HEVs employ electric propulsion systems using a combination of reduction gear and interior permanent magnet synchronous motors (IPMSM) operated by relatively high-speed more than 12 000 r/min, resulting in achieving high torque and power densities simultaneously. In the combination, since all rare-earth permanent magnets are embedded in its rotor core, a machine design of high-speed IPMSM tends to be difficult. This is due to a design confliction between keeping enough mechanical strength of the rotor core and bringing out better electromagnetic performances. To cope with this problem, this paper deals with a 6-slot-8-pole hybrid excitation flux switching machine, in which both permanent magnets and wound field excitation are employed as magnetomotive force sources. This machine has all active parts on the stator body and a rugged rotor structure similar to that of switched reluctance motor suitable for high-speed operation. Some design parameter refinements are conducted to the machine in order to elevate maximum torque capability and maximum power density as much as possible under given design requirements and constraints. As a result, it is demonstrated that the machine designed becomes a good candidate for the target HEV drive application.
180 citations
TL;DR: An overview of Heusler compounds, focusing on their structure, properties, and potential applications, can be found in this article, with a focus on the X2YZ compound.
Abstract: The class of Heusler compounds, including the XYZ and the X2YZ compounds, has not only an endless number of members, but also a vast variety of properties can be found in this class of materials, ranging from semiconductors, half-metallic ferromagnets, superconductors, and topological insulators to shape memory alloys. With this review article, we would like to provide an overview of Heusler compounds, focusing on their structure, properties, and potential applications.
172 citations
TL;DR: The paper developed an improved analytical subdomain model for predicting the open-circuit magnetic field in surface-mounted permanent magnet machines accounting for the tooth-tips in the slots that is more accurate, especially for the machines having larger slot opening width compared with tooth-tip height.
Abstract: The paper developed an improved analytical subdomain model for predicting the open-circuit magnetic field in surface-mounted permanent magnet machines accounting for the tooth-tips in the slots. The whole field domain is divided into four types of simple subdomains, viz. magnets, air-gap, slot openings, and slots. The analytical expression of each subdomain is derived and the field solution is obtained by applying the boundary conditions and interface conditions between subdomains. Compared with the conventional subdomain models, the subdomain model accounting for tooth-tips can accurately predict the flux density inside the slots. Based on the developed field model, the cogging torque is computed by the Maxwell stress tensor. The finite element analysis is carried out to validate the analytical model. It shows that the developed subdomain model accounting for tooth-tips is more accurate, especially for the machines having larger slot opening width compared with tooth-tip height.
159 citations
TL;DR: A detailed comparison of the characteristics of five different rotor topologies for a distributed winding permanent-magnet (PM) machine for high-performance traction applications, including hybrid electric vehicles is presented.
Abstract: This paper presents a detailed comparison of the characteristics of five different rotor topologies for a distributed winding permanent-magnet (PM) machine for high-performance traction applications, including hybrid electric vehicles. These rotor topologies include one surface PM topology and four single-layer interior PM topologies (conventional, segmented, V shape, and W shape). The performance characteristics, which include the back-electromotive force and its harmonics, magnet mass, iron loss, and ripple torque are compared and analyzed. A 7.5-kW interior permanent-magnetic (IPM) prototype using the conventional rotor topology was tested and the finite-element analysis results were compared. The aim of the paper is to give some guidance and reference for machine designers who are interested in IPM machine selection for high-performance traction applications.
157 citations
TL;DR: In this paper, the possibility of replacing a mechanical planetary gear system by a magnetic planetary gearbox has been explored, which has many advantages such as contact-free, no gear lubrication, high speed reduction ratio and high durability.
Abstract: The paper deals with the possibility of replacing a mechanical planetary gear system by a magnetic planetary gearbox. The magnetic planetary gearbox has many advantages such as contact-free, no gear lubrication, high-speed-reduction ratio and high durability. Firstly, the principle of operation, design equations and Willis relation for the magnetic and the mechanical planetary gears are given. A comparative study between the two systems in terms of torque transmission capabilities is presented.
156 citations
TL;DR: In this article, an axial field flux-switching permanent magnet (AFFSPM) machine with a doubly-salient structure is presented as a wind power generator.
Abstract: A novel axial field flux-switching permanent magnet (AFFSPM) machine with a doubly-salient structure is presented as a wind power generator. One rotor is sandwiched between two stators in which both windings and permanent magnets are placed. This novel generator is suitable for the wind power generation system because of its shorter axial length and higher power density. A three-phase 12/10-pole 0.6 kW AFFSPM generator is designed. The power-size equation of the machine is deduced, and the size of generator is determined. Based on the 3-D finite element method, the electromagnetic performances of the generator are investigated. According to the theoretical calculation, a prototype is manufactured and the experiments are done. The analysis results are consistent with the experimental ones well.
130 citations
TL;DR: In this paper, a general class of models of vector magnetizations with hysteresis that form a natural extension of the classical Scalar Preisach Model is defined, which can be extended to the 3D case as well.
Abstract: This paper deals with the modeling of vector fields that exhibit hysteresis. A general class of models of vector magnetizations with hysteresis that form a natural extension of the Classical Scalar Preisach Model is defined. Although the modeling was done for the 2-d case, the same theory can be extended to the 3-d case as well. After reviewing some general properties of conservative fields, the specific case of unit magnitude vector fields is discussed. The paper focuses on discussing the properties of a general vector hysteresis operator (hysteron). The mathematical approach followed here can be applied not only to the magnetic hysteresis, but also to any hysteresis process. Some examples of vector hysterons, deduced from the general definition, are presented and their properties analyzed.
127 citations
TL;DR: In this article, the authors show that if partially hydrogenated LaFe13-x-6Hz alloys are held at their Curie temperature for several days, they decomposes into a fraction with an increased curie temperature and another one with decreased Curie temperatures compared to the starting material, and that these degrading materials cannot be used in applications which require constant properties over a long period of time.
Abstract: Long-term aging treatments of partially hydrogenated ternary La-Fe-Si alloys show that these materials do not have stable magnetic properties. If partially hydrogenated LaFe13- xSixHz is held at its Curie temperature for several days it decomposes into a fraction with an increased Curie temperature and another one with decreased Curie temperature compared to the starting material. Such degrading material cannot be used in applications which require constant properties over a long period of time. By fully hydrogenating manganese containing LaFe13-x-yMnySixHz, stable alloys with adjustable Curie temperatures around room temperature can be produced. These hydrides do not change their magnetic properties if they are operated close to their Curie temperature.
TL;DR: In this paper, a micro energy-harvesting device using an iron-gallium alloy (Galfenol), capable of generating electrical energy from ambient vibrations, was proposed.
Abstract: We propose a micro energy-harvesting device, using an iron-gallium alloy (Galfenol), capable of generating electrical energy from ambient vibrations. Galfenol is a ductile magnetostrictive material with a high piezomagnetic constant, good machinability, and a large inverse magnetostrictive effect by which magnetization can be varied by mechanical stress. The device consists of two beams of Galfenol combined with iron yokes, coils, and a bias magnet. A bending force applied at the tip of the cantilever yields a flux increase by tensile stress in one beam, and a flux decreases in the other by compression. The time variation of the flux generates a voltage on the wound coils. This energy harvester has advantages over conventional types of device, such as those using piezoelectric materials, with respect to size, and efficiency, and it has high robustness and low electrical impedance. In addition, the structure needs only a low mechanical force to generate electricity. In this paper, the free vibration characteristic to accrue electric energy effectively is examined. From the experimental results, the energy conversion efficiency in the vibration is inverse proportional to the resonant frequency.
TL;DR: It is confirmed that the changes in the bio-magnetic field activity precisely synchronized with extracellular electric activity for stomach musculature of the guinea-pig, and it is shown that Ca2+ channel activity of the smooth muscle tissue can be evaluated using the MI sensor.
Abstract: New measured results of spontaneous oscillatory bio-magnetic field generated from preparations of guinea-pig smooth muscle tissue are presented in this paper using the pico-Tesla MI sensor. It is confirmed that the changes in the bio-magnetic field activity precisely synchronized with extracellular electric activity for stomach musculature of the guinea-pig. It is, however, noteworthy that these two activities provide different biological information. A phase lag of around 2 s of the magnetic signal pulse against the extracellular electric signal pulse is newly found. It is also shown that Ca2+ channel activity of the smooth muscle tissue (taenia caeci) can be evaluated using the MI sensor. Both electric and magnetic activities depend on the functionality of the living tissues. Therefore, the pico-Tesla MI sensor has the potential for non-invasive detection use in wide range of biology and medicine, including non-invasive evaluation use of the stem cells development.
TL;DR: In this article, an equivalent thermal model of a stator slot is derived from a homogenization of the winding, and a discretization is achieved using the finite integration technique considering transient analysis.
Abstract: The aim of the method detailed in this paper is to get an equivalent thermal model of a stator slot, in order to simplify the calculation of desired temperatures in an electrical machine winding. This study is divided in two steps: First, the equivalent thermal conductivity is deduced from a homogenization of the winding, and next, a discretization is achieved using the finite integration technique considering transient analysis. In order to evaluate the method, results from the equivalent model are compared with finite element simulations considering two slot geometries.
TL;DR: In this paper, a linear permanent magnet (PM) machine for direct-drive wave energy harvesting by using a linear magnetic gear was proposed, where the slow reciprocating wave motion is directly captured by the low-speed mover of the gear, and then amplified in speed via the gear to actuate the generator, hence producing higher output voltage.
Abstract: This paper proposes a linear permanent magnet (PM) machine for direct-drive wave energy harvesting by using a linear magnetic gear. The proposed machine consists of a linear magnetic gear cascaded with a linear PM generator in which the high-speed mover of the linear magnetic gear and the translator of the PM generator artfully shares with the same shaft. In short, the slow reciprocating wave motion is directly captured by the low-speed mover of the gear, and then amplified in speed via the gear to actuate the generator, hence producing higher output voltage. By using finite element analysis, the steady and dynamic performances are analyzed, which confirms that the proposed machine can offer higher power density and higher efficiency than its counterpart.
TL;DR: This paper presents a new class of linear permanent magnet (PM) vernier machines which is suitable for low speed and high thrust force applications and is analyzed and verified by using the finite element method.
Abstract: This paper presents a new class of linear permanent magnet (PM) vernier machines which is suitable for low speed and high thrust force applications. The machine is composed of a tubular stator and a tubular translator. The stator consists of an iron core with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of stator teeth. The translator is designed as a simple tubular iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed machine are analyzed and verified.
TL;DR: In this paper, the authors developed a general design guideline for split-slot low-speed Vernier permanent magnet (VPM) machines, generalize the operation principle, and illustrate the relationship among the numbers of the stator slots, coil poles, permanent magnet pole pairs, thereby laying a solid foundation for the design of various kinds of VPM machines.
Abstract: Vernier permanent magnet (VPM) machines can be utilized for direct drive applications by virtue of their high torque density and high efficiency. The purpose of this paper is to develop a general design guideline for split-slot low-speed VPM machines, generalize the operation principle, and illustrate the relationship among the numbers of the stator slots, coil poles, permanent magnet (PM) pole pairs, thereby laying a solid foundation for the design of various kinds of VPM machines. Depending on the PM locations, three newly designed VPM machines are reported in this paper and they are referred to as 1) rotor-PM Vernier machine, 2) stator-tooth-PM Vernier machine, and 3) stator-yoke-PM Vernier machine. The back-electromotive force (back-EMF) waveforms, static torque, and air-gap field distribution are predicted using time-stepping finite element method (TS-FEM). The performances of the proposed VPM machines are compared and reported.
TL;DR: In this paper, a modular permanent magnet vernier machine (PMVM) was proposed for direct drive applications, which decouples each phase and suppresses the magnetic unbalance caused by the consequent pole rotor.
Abstract: The permanent magnet vernier machine (PMVM) is known to be well suited for direct drive applications due to its high torque characteristics at low speed. This paper introduces a novel design of PMVM comprising a modular stator and a consequent pole rotor. The proposed design magnetically decouples each phase and suppresses the magnetic unbalance caused by the consequent pole rotor.
TL;DR: Key challenges and recent advances for enabling embedded STT-MRAM on a deeply scaled CMOS logic platform are addressed.
Abstract: Spin-transfer-torque magnetoresistive random access memory (STT-MRAM) has been considered a promising technology for future mobile system-on-chip memories due to negligible static leakage power, high-speed read/write operations, and unlimited read/write endurance. In this paper, we address key challenges and recent advances for enabling embedded STT-MRAM on a deeply scaled CMOS logic platform.
TL;DR: In this article, a high force density linear electromagnetic actuator based on the concept of magnetic screw-nut is described, in which helically disposed, radially magnetized permanent magnets are placed on both the screw and the nut.
Abstract: This paper describes a high force density linear electromagnetic actuator based on the concept of magnetic screw-nut, in which helically disposed, radially magnetised permanent magnets are placed on both the screw and the nut. Magnetic force and torque can be developed between the two parts without direct mechanical contact. Analytical and numerical analysis has been carried to predict the performance of the magnetic screw-nut assembly. It has been shown that a thrust force density in excess of 10 MN/m3 can be achieved for airgap lengths varying from 0.4 mm to 0.8 mm and a lead λ greater than 7 mm. When combined with a naturally cooled permanent magnet brushless machine having a torque density of ~15 kNm/m3, the resulting thrust force density of the combined system, i.e. electrical machine and magnetic screw-nut assembly, is an order of magnitude higher than that of a liquid-cooled tubular permanent magnet brushless machine.
TL;DR: In this article, a subdomain model considering the influence of tooth-tips is developed for predicting the armature reaction field in surface-mounted permanent-magnet machines having either non-overlapping or overlapping windings.
Abstract: A subdomain model considering the influence of tooth-tips is developed for predicting the armature reaction field in surface-mounted permanent-magnet machines having either non-overlapping or overlapping windings. In the developed model, the field domain is divided into three types of subdomains, viz. air gap including magnet, slot openings, and slots. The expression of the vector potential distribution in each subdomain is obtained by the variable separation method, and the field solution is obtained by applying the boundary and interface conditions. Compared with the conventional subdomain model, the subdomain model considering the tooth-tips predicts similar flux density in the air gap and magnets, but exhibits much higher accuracy for the flux density in the slot openings and slots. The finite-element results validate the analytical prediction.
TL;DR: A novel semianalytical model for cogging torque computation in PMSMs is proposed and based on the proposed model, a multiobjective optimization framework is developed and the particle swarm optimization (PSO) method is applied to find the optimum machine design.
Abstract: Magnet segmentation is an effective and simple technique for cogging torque reduction in high power permanent-magnet (PM) synchronous machines; however, it deteriorates air gap flux density and decreases the output torque. Therefore, a multiobjective optimization framework is necessary for cogging torque minimization, and to diminish its adverse effect on the output torque in segmented-pole permanent-magnet synchronous machines (PMSMs). This can be fulfilled by proper selection of widths and displacements of the magnet segments. Finite-element analysis (FEA) is an accurate method for this purpose. However, it is very time consuming where finding optimal configuration needs a lot of simulations. Thus, an analytical based design optimization is very useful and eases the design process. In this paper, a novel semianalytical model for cogging torque computation in PMSMs is proposed. Based on the proposed model, a multiobjective optimization framework is developed. The particle swarm optimization (PSO) method is applied to find the optimum machine design. To show the effectiveness of the proposed method, two prototype segmented magnet PMSMs with two and three PM blocks per pole are optimized respectively. Performance characteristics are compared to the initial machine design and segmented PMSMs with design parameters chosen according to previous analytical models and initial uniform pole machines using FEA.
TL;DR: The contradictory effects of a large value of magnetizing inductance in improving early start-up and deteriorating synchronization of line-start permanent magnet synchronous motors are analyzed and some design guidelines are proposed for the proper selection of the magnetizing induction in motor designs for different applications.
Abstract: The capabilities of proper start-up and synchronization are important issues in the design of line-start permanent magnet synchronous motors. Failing in early start-up or in synchronization under certain conditions prevents the widespread use of these motors. In order to draw useful guidelines for the design of line-start permanent magnet synchronous motors, the contradictory effects of a large value of magnetizing inductance in improving early start-up and deteriorating synchronization of line-start permanent magnet synchronous motors are analyzed in this paper. The analysis is done through three different methods. First, the effect of magnetizing inductance on average and pulsating torques of the motors during asynchronous operation is investigated and the role of these torques in start-up and synchronization performances of the motors is discussed. A critical load is then determined in terms of motors parameters as a torque limit above which the motors cannot start. The effect of magnetizing inductance, magnet flux, and saliency on the critical load is also investigated. A dynamic d-q model of the motors is then implemented to support the discussions by analyzing two line start motors with different magnetizing inductances. Finite-element-based analyses are then carried out for both motors to consider motors parameters variation, skin effect, saturation, rotor asymmetry, and cross magnetization. A good agreement between the finite-element method and dynamic simulation results is evident. Finally, some design guidelines are proposed for the proper selection of the magnetizing inductance in motor designs for different applications.
TL;DR: In this article, the authors proposed a method for reducing cogging torque in surface-mounted permanent magnet motors with nonuniformly distributed teeth, where the width of one tooth tip is different from that of the others while all slot openings are the same.
Abstract: This paper proposed a novel method for reducing cogging torque in surface-mounted permanent-magnet (PM) motors with nonuniformly distributed teeth. In this method, the width of one tooth tip is different from that of the others while all slot openings are the same. By suitable selection of the teeth width ratio, i.e., the width ratio of the one tooth tip to others, the cogging torque can be greatly reduced. First, the analytical expression of cogging torque was deduced and used to analyze the cogging torque qualitatively. Based on the above, analytical method was proposed to determine the teeth width ratio. To determine the teeth width ratio accurately, numerical method was proposed. Calculation of cogging torque by finite element method (FEM) shows that cogging torque can be greatly reduced by teeth width ratio determined by analytical method, and the teeth width ratio determined by numerical method can reduce the cogging torque further, which proved the effectiveness of the proposed methods. At last, the influences of the stator asymmetry resulted by this method on PM motors were discussed.
TL;DR: In this article, the origins and mathematical derivations of the noise sources in magnetic tunnel junction (MTJ) sensors are presented, illustrating how different factors affecting the performance of MTJ sensors.
Abstract: Noise problem limits the sensitivity of magnetic tunnel junction (MTJ) sensors for ultra-low magnetic field applications. Noise analysis not only helps in finding ways to eliminate noise disturbances but also essential for understanding the electronic and magnetic properties of MTJs. These approaches provide insight for optimizing the design of MTJ sensors before fabrication. This paper reviews the noise sources in MTJ sensors reported in recent years. Both the origins and mathematical derivations of the noise sources are presented, illustrating how different factors affecting the performance of MTJ sensors. A brief outlook of challenges in the future is also given.
TL;DR: A recursive approach is proposed that is promising for estimating the trajectory and the magnetic moment components of a target modeled as a magnetic dipole source using data collected with a gradiometer using the unscented Kalman filter to generate the prior distribution of the unknown parameters.
Abstract: Previous magnetic dipole localization algorithms using gradient data attempt to find the position of the magnetic source at the measurement time only. Based on the direct inversion of the magnetic gradient tensor, these methods provide results that can be highly sensitive to temporal noise in data. To avoid a temporally scattered solution, a recursive approach is proposed that is promising for estimating the trajectory and the magnetic moment components of a target modeled as a magnetic dipole source using data collected with a gradiometer. In this study, the determination of target position, magnetic moment, and velocity is formulated as a Bayesian estimation problem for dynamic systems, which could be solved using a sequential Monte Carlo based approach known as the “particle filter.” This filter represents the posterior distribution of the state variables by a system of particles which evolve and adapt recursively as new information becomes available. In addition to the conventional particle filter, the proposed tracking and classification algorithm uses the unscented Kalman filter (UKF) to generate the prior distribution of the unknown parameters. The proposed method is then demonstrated by applying it to real data collected when an automobile was passing by a gradiometer either on a straight or a curved track. The results indicate that the recursive method is less sensitive to noise than the direct inversion solution, even if not all the components of the gradient tensor were used.
TL;DR: This work discusses how general purpose workloads can show that more than 93% of device blocks can remain unchanged over a day, and that for more specialized workloads less than 0.5% of a shingled-write disk's capacity would be needed to hold randomly updated blocks.
Abstract: Ultimately the performance and success of a shingled write disk (SWD) will be determined by more than the physical hardware realized, but will depend on the data layouts employed, the workloads experienced, and the architecture of the overall system, including the level of interfaces provided by the devices to higher levels of system software. While we discuss several alternative layouts for use with SWD, we also discuss the dramatic implications of observed workloads. Example data access traces demonstrate the surprising stability of written device blocks, with a small fraction requiring multiple updates (the problematic operation for a shingled-write device). Specifically, we discuss how general purpose workloads can show that more than 93% of device blocks can remain unchanged over a day, and that for more specialized workloads less than 0.5% of a shingled-write disk's capacity would be needed to hold randomly updated blocks. We further demonstrate how different approaches to data layout can alternatively improve or reduce the performance of a shingled-write device in comparison to the performance of a traditional non-shingled device.
TL;DR: In this paper, a thermally assisted switching (TAS) MTJ cell and a pre-charge sensing amplifier (PCSA) circuit are used to overcome the low reliability in memory cell and sensing amplifier circuits, which greatly limits its practical applications for logic computation.
Abstract: Recently, ultra-low power circuits based on logic-in magnetic tunnel junction (MTJ) memory structure have been studied thanks to its non-volatility, infinite endurance, high access speed, and easy integration with CMOS process. However, this type of circuit suffers from low reliability both in memory cell and sensing amplifier circuits, which greatly limits its practical applications for logic computation. In this paper, we present a new design of magnetic full adder (MFA) to overcome this issue based on the thermally assisted switching (TAS) MTJ cell and pre-charge sensing amplifier (PCSA) circuit. By using CMOS 65 nm design kit and a precise TAS-MTJ model, mixed simulations have been performed to demonstrate its high reliability keeping low power and small die area.
TL;DR: In this article, strip-line inductors integrated with Ni80Fe20 were fabricated, electrically characterized, and compared to models, and electrical characterization included frequency dependent measurements of effective self and mutual inductance, effective resistance, coupling coefficient, and saturation effects.
Abstract: On-chip strip-line coupled inductors integrated with magnetic material are a promising technology option to enable on-chip voltage regulators for improving power management in microelectronics. We report on design methodologies where several examples of parameter tradeoffs are presented. When considered with practical integration constraints, these result in an optimized structure. Strip-line inductors integrated with Ni80Fe20 were then fabricated, electrically characterized, and compared to models. Electrical characterization included frequency dependent measurements of effective self and mutual inductance, effective resistance, coupling coefficient, and saturation effects.
TL;DR: In this article, the influence of elastic tensile and compressive stresses of various magnitudes on the magnetic Barkhausen emissions was studied, with the objective of developing a technique for quantitative measurements of surface stress in machined steels.
Abstract: This paper describes a method for detecting stress in the surface of magnetic materials, such as steels, based on the measurement of magnetic Barkhausen emissions. The paper presents a simple practical linear calibration curve that can be used to determine stress, and also provides a theoretical explanation of the reason for such a relationship. The influence of elastic tensile and compressive stresses of various magnitudes on the magnetic Barkhausen emissions was studied, with the objective of developing a technique for quantitative measurements of surface stress in machined steels. The peak amplitude of the Barkhausen emissions was found to correlate with both residual and applied stress, showing a clear rising trend for transition from compressive to tensile stress. The relationship between stress dependence of the maximum differential anhysteretic susceptibility and Barkhausen peak amplitude was observed. Plots of reciprocal values 1/χmax' and 1/VMBN max against stress showed a linear relationship providing a convenient method for detecting stress levels in near-surface regions from Barkhausen measurements.