| 1. |
- Kirby, B. J., et al.
(författare)
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Depth-resolved magnetization reversal in nanoporous perpendicular anisotropy multilayers
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:3
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Tidskriftsartikel (refereegranskat)abstract
- We have used polarized neutron reflectometry to study the field-dependent magnetizations of Co/Pt mulitlayers patterned via deposition onto nanoporous alumina hosts with varying pore aspect ratio. Despite the porosity and lack of long-range order, robust spin-dependent reflectivities are observed, allowing us to distinguish the magnetization of the surface multilayer from that of material in the pores. We find that as the pores become wider and shallower, the surface Co/Pt multilayers have progressively smaller high field magnetization and exhibit softer magnetic reversal—consistent with increased magnetic disorder and a reduction of the perpendicular anisotropy near the pore rims. These results reveal complexities of magnetic order in nanoporous heterostructures, and help pave the way for depth-resolved studies of complex magnetic heterostructures grown on prepatterned substrates.
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| 2. |
- Mohseni, Seyed Majid, et al.
(författare)
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Spin Torque-Generated Magnetic Droplet Solitons
- 2013
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 339:6125, s. 1295-1298
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Tidskriftsartikel (refereegranskat)abstract
- Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation of their magnetic analog has been experimentally challenging. Using spin transfer torque underneath a nanocontact on a magnetic thin film with perpendicular magnetic anisotropy (PMA), we have observed the generation of dissipative magnetic droplet solitons and report on their rich dynamical properties. Micromagnetic simulations identify a wide range of automodulation frequencies, including droplet oscillatory motion, droplet "spinning," and droplet "breather" states. The droplet can be controlled by using both current and magnetic fields and is expected to have applications in spintronics, magnonics, and PMA-based domain-wall devices.
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| 3. |
- Chung, Sunjae, et al.
(författare)
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Tunable spin configuration in [Co/Ni]-NiFe spring magnets
- 2013
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 46:12, s. 125004-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a tunable spin configuration in [Co/Ni](4)/Co-NiFe exchange spring magnets. The strong perpendicular magnetic anisotropy of the Co/Ni multilayer, which competes with the in-plane shape anisotropy of the Ni81Fe19 (Py) layer, allows for unique magnetic configurations. By varying the NiFe thickness (t(NiFe)) from 2.6 to 3.0 nm, we show that the magnetization tilt angle can be easily tuned from completely out-of-plane (0 degrees) to in-plane (90 degrees). This transition, which occurs for a small range of t(NiFe), can be estimated from the major loop remanence and one-dimensional micromagnetic calculations. These tunable magnetization tilt spring magnets are highly promising for future applications in spin-transfer torque-based devices.
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| 4. |
- Davies, J. E., et al.
(författare)
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Reversal mode instability and magnetoresistance in perpendicular (Co/Pd)/Cu/(Co/Ni) pseudo-spin-valves
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:2, s. 022409-
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Tidskriftsartikel (refereegranskat)abstract
- We have observed distinct temperature-dependent magnetization reversal modes in a perpendicular (Co/Pd)(4)/Co/Cu/(Co/Ni)(4)/Co pseudo-spin-valve, which are correlated with spin-transport properties. At 300 K, magnetization reversal occurs by vertically correlated domains. Below 200 K the hysteresis loop becomes bifurcated due to laterally correlated reversal of the individual stacks. The magnetic configuration change also leads to higher spin disorders and a significant increase in the giant magnetoresistance effect. First order reversal curve measurements reveal that the coupled state can be re-established through field cycling and allow direct determination of the interlayer coupling strength as a function of temperature.
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| 5. |
- Dumas, Randy K., et al.
(författare)
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Spin-Wave-Mode Coexistence on the Nanoscale : A Consequence of the Oersted-Field-Induced Asymmetric Energy Landscape
- 2013
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 110:25, s. 257202-
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Tidskriftsartikel (refereegranskat)abstract
- It has been argued that if multiple spin wave modes are competing for the same centrally located energy source, as in a nanocontact spin torque oscillator, that only one mode should survive in the steady state. Here, the experimental conditions necessary for mode coexistence are explored. Mode coexistence is facilitated by the local field asymmetries induced by the spatially inhomogeneous Oersted field, which leads to a physical separation of the modes, and is further promoted by spin wave localization at reduced applied field angles. Finally, both simulation and experiment reveal a low frequency signal consistent with the intermodulation of two coexistent modes.
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| 6. |
- Fang, Yeyu, 1984, et al.
(författare)
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A Nonvolatile Spintronic Memory Element with a Continuum of Resistance States
- 2013
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 23:15, s. 1919-1922
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Tidskriftsartikel (refereegranskat)abstract
- A continuum of stable remanent resistance states is reported in perpendicularly magnetized pseudo spin valves with a graded anisotropy free layer. The resistance states can be systematically set by an externally applied magnetic field. The gradual reversal of the free layer with applied field and the field-independent fixed layer leads to a range of stable and reproducible remanent resistance values, as determined by the giant magnetoresistance of the device. An analysis of first-order reversal curves combined with magnetic force microscopy shows that the origin of the effect is the field-dependent population of up and down domains in the free layer.
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| 7. |
- Tacchi, S., et al.
(författare)
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Spin wave excitations in exchange-coupled [Co/Pd]-NiFe films with tunable tilting of the magnetization
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:14, s. 144426-
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Tidskriftsartikel (refereegranskat)abstract
- Brillouin light scattering was applied to measure the evolution of spin waves in exchange-coupled [Co/Pd]-NiFe films with out-of-plane/in-plane magnetic anisotropy. Tunable tilting of the magnetization has important effects on the spin wave frequency gap: a substantial increase is observed with decreasing the soft NiFe thickness, while seemingly insignificant tilting angles cause a strong reduction with respect to a film with only the hard [Co/Pd] component. The spin wave frequency is reproduced also in samples, with increased thickness of the upper Pd layer, where a sudden modification in the tilting at the hard/soft interface is caused by the weakening of interlayer exchange.
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