Change search
ReferencesLink to record
Permanent link

Direct link
Quantitative magnetic characterization of synthetic ferrimagnets for predictive spin-dynamic behavior
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, 6971569Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2014. Vol. 50, no 11, 6971569
Keyword [en]
Magnetic multilayers, magnetization reversal, microwave magnetics, spin valves
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-161498DOI: 10.1109/TMAG.2014.2316596ISI: 000349465900269ScopusID: 2-s2.0-84915820027OAI: diva2:794833

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
Electrical Engineering, Electronic Engineering, Information Engineering

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: 24 hits
ReferencesLink to record
Permanent link

Direct link