Magnetic droplet solitons in all-perpendicular nano-contact spin torque oscillators
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Spin-torque-generated magnetic droplets are nontopological solitons that have both dynamic and static characteristics. Although theoretical studies of these droplets originally dealt with an all-perpendicular magnetic system, all experimental demonstrations have so far relied on orthogonal spin valve structures that require a rather strong magnetic field to nucleate the droplet. Here, for the first time, we show the nucleation and sustained operation of magnetic droplets under a low magnetic field using nanocontact spin-torque oscillators (NC-STO), both the free Co/Ni and fixed Co/Pd multilayers of which have strong perpendicular magnetic anisotropy. Droplet nucleation is observed as a change in the NC-STO resistance and the appearance of significant broadband microwave signal generation below 1 GHz. We also observe another important phenomenon in which the nucleated magnetic droplet can transform into a skyrmionic nanobubble in the low-field regime. Both magnetic droplet solitons and skyrmionic nanobubbles have been studied in detail using micromagnetic simulation.
Condensed Matter Physics Materials Engineering
Research subject Physics; Materials Science and Engineering
IdentifiersURN: urn:nbn:se:kth:diva-191274OAI: oai:DiVA.org:kth-191274DiVA: diva2:955789
QC 201608292016-08-262016-08-262016-08-29Bibliographically approved