Magnetic droplet soliton pairs

S Jiang; S Chung; M Ahlberg; A Frisk; R Khymyn; Q Tuan Le; H Mazraati; A Houshang; O Heinonen; J Åkerman

doi:10.1038/s41467-024-46404-7

Magnetic droplet soliton pairs

Nat Commun. 2024 Mar 8;15(1):2118. doi: 10.1038/s41467-024-46404-7.

Authors

S Jiang^#^{1

2}, S Chung^#^{3

4}, M Ahlberg^#⁵, A Frisk², R Khymyn², Q Tuan Le^{2

6}, H Mazraati⁶, A Houshang², O Heinonen^{7

8}, J Åkerman^{9

10

11

12}

Affiliations

¹ School of Microelectronics, South China University of Technology, 511442, Guangzhou, China.
² Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.
³ Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden. sjchung76@knue.ac.kr.
⁴ Department of Physics Education, Korea National University of Education, Cheongju, 28173, Korea. sjchung76@knue.ac.kr.
⁵ Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden. martina.ahlberg@physics.gu.se.
⁶ Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden.
⁷ Materials Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA.
⁸ Seagate Technology, 7801 Computer Ave., Bloomington, MN, 55435, USA.
⁹ Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden. johan.akerman@physics.gu.se.
¹⁰ Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, 100 44, Stockholm, Sweden. johan.akerman@physics.gu.se.
¹¹ Center for Science and Innovation in Spintronics, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan. johan.akerman@physics.gu.se.
¹² Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan. johan.akerman@physics.gu.se.

^# Contributed equally.

Abstract

We demonstrate magnetic droplet soliton pairs in all-perpendicular spin-torque nano-oscillators (STNOs), where one droplet resides in the STNO free layer (FL) and the other in the reference layer (RL). Typically, theoretical, numerical, and experimental droplet studies have focused on the FL, with any additional dynamics in the RL entirely ignored. Here we show that there is not only significant magnetodynamics in the RL, but the RL itself can host a droplet driven by, and coexisting with, the FL droplet. Both single droplets and pairs are observed experimentally as stepwise changes and sharp peaks in the dc and differential resistance, respectively. While the single FL droplet is highly stable, the coexistence state exhibits high-power broadband microwave noise. Furthermore, micromagnetic simulations reveal that the pair dynamics display periodic, quasi-periodic, and chaotic signatures controlled by applied field and current. The strongly interacting and closely spaced droplet pair offers a unique platform for fundamental studies of highly non-linear soliton pair dynamics.