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Direct observation and imaging of a spin-wave soliton with p-like symmetry.

Bonetti S, Kukreja R, Chen Z, Macià F, Hernàndez JM, Eklund A, Backes D, Frisch J, Katine J, Malm G, Urazhdin S, Kent AD, Stöhr J, Ohldag H, Dürr HA - Nat Commun (2015)

Bottom Line: Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact.Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields.Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.

ABSTRACT
Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

No MeSH data available.


Related in: MedlinePlus

Experimental and simulated results.(a–f) Experimental time-resolved magnetization precession angle around a nanocontact spin torque oscillator (black open ellipse) measured with a scanning transmission X-ray microscope with a μ0H=60 mT magnetic field applied parallel to the x axis. The six images are 1.5 × 1.5 μm2 spatial maps, representing snapshots of the magnetization dynamics with a relative time difference of 27 ps. The black solid lines are a schematic representation of the electrical contacts of the sample. Scale bar, 200 nm. Simulated spatial maps of the magnetization precession for applied fields (g–l) μ0H=60 mT and (m–r) μ0H=80 mT. The dashed lines indicate the location where vertical cross-sections of the images was calculated, as discussed in the main text. The colour scheme is qualitatively the same for all plots, but it is quantified differently for each rows by the respective colourbar on the right side of the figure.
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f2: Experimental and simulated results.(a–f) Experimental time-resolved magnetization precession angle around a nanocontact spin torque oscillator (black open ellipse) measured with a scanning transmission X-ray microscope with a μ0H=60 mT magnetic field applied parallel to the x axis. The six images are 1.5 × 1.5 μm2 spatial maps, representing snapshots of the magnetization dynamics with a relative time difference of 27 ps. The black solid lines are a schematic representation of the electrical contacts of the sample. Scale bar, 200 nm. Simulated spatial maps of the magnetization precession for applied fields (g–l) μ0H=60 mT and (m–r) μ0H=80 mT. The dashed lines indicate the location where vertical cross-sections of the images was calculated, as discussed in the main text. The colour scheme is qualitatively the same for all plots, but it is quantified differently for each rows by the respective colourbar on the right side of the figure.

Mentions: The resulting XMCD images of precessing nonlinear spin waves are shown in Fig. 2. The black solid lines show the outline of the topological features of the nanocontact (ellipse) and the electrical connections. XMCD can clearly image the magnetic layer buried below (see Methods for details). The colour scale represents the size of the XMCD signal and corresponds to the out-of-plane precession angle (corresponding to the polar angle θ in spherical coordinates), proportional to the z-component of the magnetization. The magnetic contrast is observed only when a current IDC is injected into the permalloy layer (providing the spin torque necessary to excite the spin wave) and when the frequency of the spin-wave excitation is locked by an alternating current Imw synchronized to the X-ray pulses.


Direct observation and imaging of a spin-wave soliton with p-like symmetry.

Bonetti S, Kukreja R, Chen Z, Macià F, Hernàndez JM, Eklund A, Backes D, Frisch J, Katine J, Malm G, Urazhdin S, Kent AD, Stöhr J, Ohldag H, Dürr HA - Nat Commun (2015)

Experimental and simulated results.(a–f) Experimental time-resolved magnetization precession angle around a nanocontact spin torque oscillator (black open ellipse) measured with a scanning transmission X-ray microscope with a μ0H=60 mT magnetic field applied parallel to the x axis. The six images are 1.5 × 1.5 μm2 spatial maps, representing snapshots of the magnetization dynamics with a relative time difference of 27 ps. The black solid lines are a schematic representation of the electrical contacts of the sample. Scale bar, 200 nm. Simulated spatial maps of the magnetization precession for applied fields (g–l) μ0H=60 mT and (m–r) μ0H=80 mT. The dashed lines indicate the location where vertical cross-sections of the images was calculated, as discussed in the main text. The colour scheme is qualitatively the same for all plots, but it is quantified differently for each rows by the respective colourbar on the right side of the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4660209&req=5

f2: Experimental and simulated results.(a–f) Experimental time-resolved magnetization precession angle around a nanocontact spin torque oscillator (black open ellipse) measured with a scanning transmission X-ray microscope with a μ0H=60 mT magnetic field applied parallel to the x axis. The six images are 1.5 × 1.5 μm2 spatial maps, representing snapshots of the magnetization dynamics with a relative time difference of 27 ps. The black solid lines are a schematic representation of the electrical contacts of the sample. Scale bar, 200 nm. Simulated spatial maps of the magnetization precession for applied fields (g–l) μ0H=60 mT and (m–r) μ0H=80 mT. The dashed lines indicate the location where vertical cross-sections of the images was calculated, as discussed in the main text. The colour scheme is qualitatively the same for all plots, but it is quantified differently for each rows by the respective colourbar on the right side of the figure.
Mentions: The resulting XMCD images of precessing nonlinear spin waves are shown in Fig. 2. The black solid lines show the outline of the topological features of the nanocontact (ellipse) and the electrical connections. XMCD can clearly image the magnetic layer buried below (see Methods for details). The colour scale represents the size of the XMCD signal and corresponds to the out-of-plane precession angle (corresponding to the polar angle θ in spherical coordinates), proportional to the z-component of the magnetization. The magnetic contrast is observed only when a current IDC is injected into the permalloy layer (providing the spin torque necessary to excite the spin wave) and when the frequency of the spin-wave excitation is locked by an alternating current Imw synchronized to the X-ray pulses.

Bottom Line: Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact.Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields.Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Stanford University, Stanford, California 94305, USA.

ABSTRACT
Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

No MeSH data available.


Related in: MedlinePlus