Change search
ReferencesLink to record
Permanent link

Direct link
Nonlinear dynamics in spin vortex pairs with strong core-core coupling
KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.ORCID iD: 0000-0002-9993-4748
KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.ORCID iD: 0000-0003-2339-1692
2014 (English)In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 50, no 11, 6971321Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2014. Vol. 50, no 11, 6971321
Keyword [en]
Microwave spectra, nonlinear dynamics, rotational and gyrational resonances, spin vortex pairs
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-161496DOI: 10.1109/TMAG.2014.2327157ISI: 000349465900272ScopusID: 2-s2.0-84916204514OAI: diva2:794873

QC 20150313

Available from: 2015-03-13 Created: 2015-03-12 Last updated: 2016-05-24Bibliographically approved
In thesis
1. Static and dynamic properties of uniform- and vortex-states in synthetic nanomagnets
Open this publication in new window or tab >>Static and dynamic properties of uniform- and vortex-states in synthetic nanomagnets
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Synthetic antiferromagnets (SAFs) consist of two thin ferromagnetic particles separated by a thin nonmagnetic spacer. The magnetic moments of the two particles couple antiparallel via dipolar interactions, with the interlayer exchange interaction suppressed by a suitable choice of the spacer material. The SAF system studied in this thesis contains thin elliptical-in-the-plane permalloy particles magnetized uniformly and mutually antiparallel in the ground state. A SAF can also exhibit long-lived metastable nonuniform magnetization states, such as spin-vortex pairs. The thesis explores hysteresis and spin dynamics in: (i) uniformly magnetized SAFs and (ii) SAFs in the vortex-pair state.

The uniformly magnetized antiparallel ground state of a symmetrical SAF, having identical ferromagnetic particles, is double  degenerate. The resonance modes are in-phase (acoustical) and out-of-phase (optical) oscillations of the magnetic moments. Asymmetry between the two magnetic layers is shown to lift the degeneracy of the antiparallel ground state, which in the static regime results in unequal stability of the two states. In the dynamic regime, the asymmetries are shown to result in a splitting of the resonance frequency of the new non-degenerate ground states. The resulting resonant-mode splitting can be used to selectively switch between the antiparallel ground states by resonant microwave or thermal activation of the system.

The static and dynamic properties of the vortex pairs in SAFs were found to be strongly dependent on the relative orientation of the vortex chiralities and vortex-core polarizations in the two ferromagnetic particles of the SAF. For parallel core polarizations, a strong monopole-like core-core interaction is found to dominate the magnetic properties of the system, increasing the characteristic resonance frequency by an order of magnitude.  Analytical theory and numerical micromagnetic simulations are used to explain the measured responses.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 74 p.
National Category
Condensed Matter Physics
Research subject
urn:nbn:se:kth:diva-187473 (URN)978-91-7729-018-6 (ISBN)
Public defence
2016-06-15, FB54, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Swedish Research Council, 2014-4548Stiftelsen Olle Engkvist Byggmästare, 2014-STE

QC 20160524

Available from: 2016-05-24 Created: 2016-05-24 Last updated: 2016-05-25Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Koop, Björn C.Korenivski, Vladislav
By organisation
Nanostructure Physics
In the same journal
IEEE transactions on magnetics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 22 hits
ReferencesLink to record
Permanent link

Direct link