Header logo is

{Direct observation of Zhang-Li torque expansion of magnetic droplet solitons}

2018

Article

mms


Magnetic droplets are nontopological dynamical solitons that can be nucleated in nanocontact based spin torque nano-oscillators (STNOs) with perpendicular magnetic anisotropy free layers. While theory predicts that the droplet should be of the same size as the nanocontact, its inherent drift instability has thwarted attempts at observing it directly using microscopy techniques. Here, we demonstrate highly stable magnetic droplets in all-perpendicular STNOs and present the first detailed droplet images using scanning transmission X-ray microscopy. In contrast to theoretical predictions, we find that the droplet diameter is about twice as large as the nanocontact. By extending the original droplet theory to properly account for the lateral current spread underneath the nanocontact, we show that the large discrepancy primarily arises from current-in-plane Zhang-Li torque adding an outward pressure on the droplet perimeter. Electrical measurements on droplets nucleated using a reversed current in the antiparallel state corroborate this picture.

Author(s): Chung, S. and Tuan Le, Q. and Ahlberg, M. and Awad, A. A. and Weigand, M. and Bykova, I. and Khymyn, R. and Dvornik, M. and Mazraati, H. and Houshang, A. and Jiang, S. and Nguyen, T. N. A. and Goering, E. and Schütz, G. and Gräfe, J. and \AAkerman, Johan
Journal: {Physical Review Letters}
Volume: 120
Number (issue): 21
Year: 2018
Publisher: American Physical Society

Department(s): Modern Magnetic Systems
Bibtex Type: Article (article)

Address: Woodbury, N.Y.
DOI: 10.1103/PhysRevLett.120.217204
Language: eng

BibTex

@article{escidoc:0024,
  title = {{Direct observation of Zhang-Li torque expansion of magnetic droplet solitons}},
  author = {Chung, S. and Tuan Le, Q. and Ahlberg, M. and Awad, A. A. and Weigand, M. and Bykova, I. and Khymyn, R. and Dvornik, M. and Mazraati, H. and Houshang, A. and Jiang, S. and Nguyen, T. N. A. and Goering, E. and Sch\"utz, G. and Gr\"afe, J. and \AAkerman, Johan},
  journal = {{Physical Review Letters}},
  volume = {120},
  number = {21},
  publisher = {American Physical Society},
  address = {Woodbury, N.Y.},
  year = {2018}
}