| 1. |
- Abrahamsson, Johan, 1977-, et al.
(författare)
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A Fully Levitated Cone-Shaped Lorentz-Type Self-Bearing Machine With Skewed Windings
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:9
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Andersson, Sebastian, et al.
(författare)
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Thermoelectrically Controlled Spin-Switch
- 2010
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2140-2143
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Bissal, Ara, 1986-, et al.
(författare)
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Comparison of two Ultra-fast actuator concepts
- 2012
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Ingår i: IEEE transactions on magnetics. - : IEEE Press. - 0018-9464 .- 1941-0069. ; 48:11, s. 3315-3318
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Bormann, Dierk, et al.
(författare)
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Reluctance Network Method for Calculating the Series Impedance Matrix of Multi-Conductor Transmission Lines
- 2013
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 49:10, s. 5270-5279
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Bormann, Dierk, et al.
(författare)
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Reluctance Network Treatment of Skin and Proximity Effects in Multi-Conductor Transmission Lines
- 2012
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 48:2, s. 735-738
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Cherepov, Sergiy, et al.
(författare)
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Micromagnetics of Spin-Flop Bilayers : S, C, and Vortex Spin States
- 2010
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2124-2127
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Cherepov, Sergiy, 1981-, et al.
(författare)
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Resonant Switching of Two Dipole-Coupled Nanomagnets
- 2010
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2112-2115
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Dumas, Randy K., et al.
(författare)
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Graded Anisotropy FePtCu Films
- 2011
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 47:6, s. 1580-1586
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Dumas, Randy K., et al.
(författare)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:6, s. 4100107-
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Dumas, Randy K., et al.
(författare)
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Recent Advances in Nanocontact Spin-Torque Oscillators
- 2014
-
Ingår i: Ieee Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 50:6
-
Tidskriftsartikel (refereegranskat)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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| 11. |
- Ferguson, Richard Matthew, et al.
(författare)
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Size-Dependent Relaxation Properties of Monodisperse Magnetite Nanoparticles Measured Over Seven Decades of Frequency by AC Susceptometry
- 2013
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 49, s. 3441-3444
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic relaxation is exploited in innovative biomedical applications of magnetic particles such as magnetic particle imaging (MPI), magnetic fluid hyperthermia, and bio-sensing. Relaxation behavior should be optimized to achieve high performance imaging, efficient heating, and good SNR in bio-sensing. Using two AC susceptometers with overlapping frequency ranges, we have measured the relaxation behavior of a series of monodisperse magnetic particles and demonstrated that this approach is an effective way to probe particle relaxation characteristics from a few Hz to 10 MHz, the frequencies relevant for MPI, hyperthermia, and sensing.
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| 12. |
- Gromov, Andrey, et al.
(författare)
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Gigahertz Sandwich Strip Inductors Based on Fe-N Films : The Effect of Flux Closure at the Flange
- 2010
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2097-2100
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Tidskriftsartikel (refereegranskat)abstract
- Planar strip inductors consisting of soft Fe-N films enclosing a conductor made of Cu are fabricated on Si substrates and exhibit 70 to 100% inductance gain at 1 Ghz with quality factors of 3 to 5. The magnetic part of the inductance is less than predicted theoretically, which is attributed to hardening of the magnetic material at the edges of the strip, where the deposition is close to 60 degrees incidence. Test films were fabricated on tilted substrates and found to develop very high anisotropy for deposition angles larger than 30 degrees. Optimizing the flux closure at the strip edges is essential for further improving the performance of sandwich strip inductors.
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| 13. |
- Heinonen, O. G., et al.
(författare)
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Decoherence, Mode Hopping, and Mode Coupling in Spin Torque Oscillators
- 2013
-
Ingår i: Ieee Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 49:7, s. 4398-4404
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Tidskriftsartikel (refereegranskat)abstract
- Spin torque oscillators (STOs) often exhibit multiple modes, leading to complex behavior. One example is mode hopping between different eigenmodes of a magnetic tunnel junction (MTJ) STO. This mode hopping is a strong function of current and angle between the magnetization in the free and fixed layers, and away from anti-parallel configuration, mode hopping can be the dominant decoherence process. Another example is the linewidth of a nanocontact STO that can be a complex non-monotonic function of temperature in regions where two or more modes are excited by the oscillators. These phenomena require a generalization of the single-mode nonlinear STO theory to include mode coupling. We derive equations describing the slow time evolution of the coupled system and show they describe a dynamically driven system, similar to other systems that exhibit mode hopping in the presence of thermal fluctuations. In our description, mode coupling also leads to additional coupling between power and phase fluctuations, which can in certain limited cases lead to longer relaxation times for power fluctuations, and consequently to larger linewidths through the nonlinear frequency shift.
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| 14. |
- Heinonen, O. G., et al.
(författare)
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Decoherence, Mode Hopping, and Mode Coupling in Spin Torque Oscillators
- 2013
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 49:7, s. 4398-4404
-
Tidskriftsartikel (refereegranskat)abstract
- Spin torque oscillators (STOs) often exhibit multiple modes, leading to complex behavior. One example is mode hopping between different eigenmodes of a magnetic tunnel junction (MTJ) STO. This mode hopping is a strong function of current and angle between the magnetization in the free and fixed layers, and away from anti-parallel configuration, mode hopping can be the dominant decoherence process. Another example is the linewidth of a nanocontact STO that can be a complex non-monotonic function of temperature in regions where two or more modes are excited by the oscillators. These phenomena require a generalization of the single-mode nonlinear STO theory to include mode coupling. We derive equations describing the slow time evolution of the coupled system and show they describe a dynamically driven system, similar to other systems that exhibit mode hopping in the presence of thermal fluctuations. In our description, mode coupling also leads to additional coupling between power and phase fluctuations, which can in certain limited cases lead to longer relaxation times for power fluctuations, and consequently to larger linewidths through the nonlinear frequency shift.
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| 15. |
- Koop, Björn C., et al.
(författare)
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Nonlinear dynamics in spin vortex pairs with strong core-core coupling
- 2014
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:11
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the dynamics of spin vortex pairs in magnetic multilayer particles, with the vortices closely spaced vertically and therefore with strong core-core coupling. We focus on the spin-dynamic behavior of the system beyond the linear small-signal regime, and on the state with antiparallel vortex chiralities and parallel cores, in which the vortex cores are strongly dipole coupled. The data show a clear transition from the dominant single rotational resonance at 2-3 GHz for small excitation field amplitudes to a dominant gyrational resonance at high excitation fields. The concomitant changes in the microwave spectra, seen as satellite resonances near the rotational peak as well as a pronounced low-frequency resonance, are interpreted as arising from the nonlinearities of the main rotational mode, which also mediate microwave power transfer from the high- to the low-frequency mode.
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| 16. |
- Koop, Björn C., et al.
(författare)
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Quantitative magnetic characterization of synthetic ferrimagnets for predictive spin-dynamic behavior
- 2014
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:11
-
Tidskriftsartikel (refereegranskat)abstract
- Geometric or magnetic asymmetries in synthetic antiferromagnetic particles give rise to ferrimagnetic-like magnetization behavior, both quasi-static and dynamic. Such asymmetries in synthetic ferrimagnets can originate from a thickness imbalance or a fringing field from the reference layer in a nanopillar stack. In this paper, we theoretically describe the effects of the corresponding magnetic asymmetry contribution on the structure's static and spin-dynamic behavior. The developed model is then used to experimentally determine the asymmetry parameters of typical nanoscale spin-flop junctions, as well as successfully describe their microwave resonant properties, such as the frequency splitting and the field dependence of the optical spin-resonance spectra.
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| 17. |
- Korenivski, Vladislav
(författare)
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RDesign of magnetic transceivers for 3-d integrated circuits
- 2014
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:11
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Tidskriftsartikel (refereegranskat)abstract
- Use of magnetic film inductors as transceiver elements for wireless transfer of power and signal communication between vertically stacked silicon integrated circuits is discussed. Two characteristic designs are compared - a vertical magnetic core with high-aspect-ratio laminations and a planar magnetic core where flux closure is achieved by a suitable design of the interchip air gap. The latter design is argued to hold a promise for 3-D circuit integration.
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| 18. |
- Korenivski, Vladislav, et al.
(författare)
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Thermally Activated Switching in Nanoscale Magnetic Tunnel Junctions
- 2010
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Ingår i: IEEE Transactions on Magnetics. - 0018-9464 .- 1941-0069. ; 46:6, s. 2101-2103
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic tunnel junctions 90 to 300 nm wide and of aspect ratio approximate to 2 are studied using high-speed pulse fields with regard to the soft-layer magnetization reversal under thermal agitation. It is found that the larger cells, 200-300 nm wide, reverse through nonuniform magnetization states with the energy barriers to thermal activation an order of magnitude smaller than those expected for single-domain magnets. The single-domain limit is reached for the smallest cells, having elliptical soft layers approximately 90 nm wide and 150-200 nm long. The magnetization decay in the small cell limit is well described by the Stoner-Wohlfarth single-domain model and the Arrhenius activation law. The results demonstrate that the penalty due to the smaller magnetic volume is compensated by a larger relative energy barrier to activation as the junction size is reduced to similar to 90 nm. This determines the important length scale for geometric scaling of such technologies as magnetic random access memory.
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| 19. |
- Krings, Andreas, et al.
(författare)
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Temperature Influence of NiFe Steel Laminations on the Characteristics of Small Slotless Permanent Magnet Machines
- 2013
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 49:7, s. 4064-4067
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Tidskriftsartikel (refereegranskat)abstract
- High performance electrical machines can operate at temperatures of 100 degrees C and beyond in rotor and stator cores. However, magnetic properties are generally measured at room temperatures around 23 degrees C to 25 degrees C according to the standards, even if it is known that the magnetization of some materials is substantially influenced by increasing temperatures. This paper investigates the thermal influence on the magnetic properties and iron losses in the stator cores of small slotless permanent magnet synchronous machines (PMSMs). The stator stack is made of thin nickel iron (NiFe) lamination sheets. Magnetic measurements of the stator core are conducted for different frequencies and flux densities at several temperatures between 25 degrees C and 105 degrees C. The obtained measurement data is afterwards used in finite element method (FEM) simulations to investigate the influence of the magnetic property change on the machine performance. For the PMSM in consideration, the FEM simulations show that an increased stator core temperature reduces the electromagnetic torque considerably; approximately 1/3 of the torque reduction due to increased rotor magnet and stator core temperatures (from 25 degrees C to 100 degrees C) can be attributed to the increased stator core temperature.
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| 20. |
- Ludwig, Frank, et al.
(författare)
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Magnetic, Structural, and Particle Size Analysis of Single- and Multi-Core Magnetic Nanoparticles
- 2014
-
Ingår i: IEEE Transactions on Magnetics. - 0018-9464 .- 1941-0069. ; 50:11
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured and analyzed three different commercial magnetic nanoparticle systems, both multi-core and single-core in nature, with the particle (core) size ranging from 20 to 100 nm. Complementary analysis methods and same characterization techniques were carried out in different labs and the results are compared with each other. The presented results primarily focus on determining the particle size-both the hydrodynamic size and the individual magnetic core size-as well as magnetic and structural properties. The used analysis methods include transmission electron microscopy, static and dynamic magnetization measurements, and Mossbauer spectroscopy. We show that particle (hydrodynamic and core) size parameters can be determined from different analysis techniques and the individual analysis results agree reasonably well. However, in order to compare size parameters precisely determined from different methods and models, it is crucial to establish standardized analysis methods and models to extract reliable parameters from the data.
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| 21. |
- Masood, Ansar, et al.
(författare)
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A New Class of Materials for Magneto-Optical Applications : Transparent Amorphous Thin Films of Fe-B-Nb and Fe-B-Nb-Y Metallic Glassy Alloys
- 2014
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:4, s. 4004005-
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Tidskriftsartikel (refereegranskat)abstract
- Optically highly transparent, soft magnetic thin films (4-18 nm thick) of Fe-B-Nb- and Fe-B-Nb-Y-based glassy metal targets were grown on quartz substrates by pulsed laser deposition, and their optical and magneto-optical properties were investigated over the visible spectrum (400-700 nm). All the films found to be fully amorphous in structure were continuous with uniform thickness and surface morphology. Their optical transmittance in the range 50%-85% was found to be film thickness dependent over the entire visible regime. The Verdet constant (V) and Faraday rotation angle (theta(f)) for different films (similar to 4-18 nm) investigated as a function of wavelength (lambda) show considerably higher values for the films of Fe-B-Nb-Y alloy as compared with those for Fe-B-Nb films, e. g., the similar to 4 nm film of Fe-B-Nb-Y alloy exhibits V similar to 49 degrees/Oe cm and theta(f)similar to 26 degrees/mu m while it decreased to similar to 29.4 degrees/Oe and similar to 11.8 degrees/mu m, respectively, for the Fe-B-Nb alloy at lambda=611 nm. A linear relationship is found for the wavelength dependence of V and theta(f) for both alloy systems. To the best of our knowledge, these values are considerably higher than those reported for any other magneto-optic material. The films are found to be soft magnetic with a high saturation moment while their magnetic coercivity values increases with thinness of the films. The observed combination of optical and magneto-optical properties of this new class of amorphous metallic films makes them viable for multifunctional magneto-optical applications.
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| 22. |
- Mertins, Hans-Christoph, et al.
(författare)
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Detection of the Magnetocrystalline Anisotropy in X-Ray Magnetic Linear Dichroism Reflection Spectra Across the Fe 3p and 2p Edges
- 2014
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:11
-
Tidskriftsartikel (refereegranskat)abstract
- The magnetocrystalline anisotropy of X-ray magnetic linear dichroism (XMLD) reflection spectra measured on single-crystalline bcc Fe films across the 3p and 2p edges are presented. The XMLD spectra were obtained from a series of reflection spectra by aligning the electric field vector of linearly polarized undulator radiation with respect to the crystal axes. Our results show the presence of a huge magnetocrystalline anisotropy in the XMLD reflection spectra. The XMLD signal is further investigated as a function of the Fe film thickness in Au/Fe/Ag/GaAs layered systems. Simulations of the reflection spectra reveal the influences of interference effects, which can enhance or diminish the XMLD signals. The measured spectra are in good agreement with ab initio calculated spectra.
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| 23. |
- Mousavi, Seyedali A., et al.
(författare)
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Differential Approach of Scalar Hysteresis Modeling Based on the Preisach Theory
- 2011
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 47:10, s. 3040-3043
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces a differential approach to model scalar hysteresis based on the Preisach theory. This model can generate hysteresis trajectories for both symmetrical and asymmetrical minor loops and keep the memory of a material in a proper manner. It can easily be inverted, it has a simple algorithm with suitable computational speed, and is not memory consuming. Also, the obtained results of the model are in very good agreement with measurements.
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| 24. |
- Muduli, Pranaba, et al.
(författare)
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Modulation of Individual and Mutually Synchronized Nanocontact-Based Spin Torque Oscillators
- 2011
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Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 47:6, s. 1575-1579
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Tidskriftsartikel (refereegranskat)abstract
- We study current modulation of spin torque oscillators (STOs) based on single and double nano-contacts. For single nano-contact devices, we show modulation for a carrier frequency of 19-40 GHz and modulation frequencies from 50 MHz to 1 GHz. We show that the behavior of modulation and the asymmetry in the power of the modulation sidebands can be very well modeled, and predicted, using nonlinear frequency and amplitude modulation (NFAM) calculations based on the free-running STO parameters. Modulation of synchronized double nano-contact STOs is equally well modeled by NFAM theory and demonstrates the feasibility of communication applications based on arrays of synchronized STOs.
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| 25. |
- Nguyen, Thi Ngoc Anh, et al.
(författare)
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Investigation of the Tunability of the Spin Configuration Inside Exchange Coupled Springs of Hard/Soft Magnets
- 2014
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 50:6, s. 2004906-
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic multilayer (ML) structures comprising a perpendicular magnetic anisotropy (PMA) layer coupled to an in-plane magnetic anisotropy (IMA) layer are promising materials for zero/low field operating spin-torque oscillators and bit patterned recording media. The magnetization tilt angle can be easily tuned by varying the IMA layer thickness due to the competition between PMA and IMA layers. To explore the underlying magnetization reversal mechanism and to further understand the control of tilt angle and uniformity of the magnetization, the IMA (NiFe, Co, and CoFeB)/PMA (Co/Pd MLs) exchange spring systems are systematically studied. Experimental data obtained from magnetometry show good agreement with 1-D micromagnetic simulations, allowing us to design tunable exchange coupled spring as a function of IMA thickness.
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