Spin transfer torque generated magnetic droplet solitons (invited)
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 17, 172612- p.Article in journal (Refereed) Published
We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90 degrees, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy.
Place, publisher, year, edition, pages
2014. Vol. 115, no 17, 172612- p.
Polarized Current, Nano-Oscillators, Electric-Current, Phase-Locking, Driven, Modulation, Multilayer, Excitation, Devices, Emission
IdentifiersURN: urn:nbn:se:kth:diva-146138DOI: 10.1063/1.4870696ISI: 000335643700581ScopusID: 2-s2.0-84903892219OAI: oai:DiVA.org:kth-146138DiVA: diva2:723172
FunderEU, FP7, Seventh Framework Programme, ICT-257159 "MACALO"Swedish Foundation for Strategic Research Swedish Research CouncilKnut and Alice Wallenberg Foundation
QC 201406102014-06-102014-06-092014-11-13Bibliographically approved