Spin transfer torque generated magnetic droplet solitons

Sunjae Chung, Seyed Majid Mohseni, Sohrab R. Sani, Ezio Iacocca, Randy K. Dumas, T. N. Anh Nguyen, Ye Pogoryelov, P. K. Muduli, Anders Eklund, Mark Hoefer, Johan Akerman

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Abstract

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°, 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.
Original languageEnglish
Article number172612
JournalJournal of Applied Physics
Volume115
Issue number17
Early online date16 Apr 2014
DOIs
Publication statusPublished - 7 May 2014
Externally publishedYes

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