Magnetic droplet nucleation boundary in orthogonal spin-torque nano-oscillators

• Published in: Nature communications Vol. 7; no. 1; pp. 11209 - 8
• Main Authors: Chung, Sunjae, Eklund, Anders, Iacocca, Ezio, Mohseni, Seyed Majid, Sani, Sohrab R., Bookman, Lake, Hoefer, Mark A., Dumas, Randy K., Åkerman, Johan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.04.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 142/126; 639/301/119/1001; 639/301/119/997; Anisotropy; Computer Systems; Condensed Matter Physics; Datorsystem; Den kondenserade materiens fysik; Humanities and Social Sciences; multidisciplinary; Nano-technology; Nanoteknik; Nucleation; Science; Science (multidisciplinary); Stability analysis
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms11209

Static and dynamic magnetic solitons play a critical role in applied nanomagnetism. Magnetic droplets, a type of non-topological dissipative soliton, can be nucleated and sustained in nanocontact spin-torque oscillators with perpendicular magnetic anisotropy free layers. Here, we perform a detailed experimental determination of the full droplet nucleation boundary in the current–field plane for a wide range of nanocontact sizes and demonstrate its excellent agreement with an analytical expression originating from a stability analysis. Our results reconcile recent contradicting reports of the field dependence of the droplet nucleation. Furthermore, our analytical model both highlights the relation between the fixed layer material and the droplet nucleation current magnitude, and provides an accurate method to experimentally determine the spin transfer torque asymmetry of each device. Magnetic droplets occur in nanocontact spin-torque oscillators with perpendicular anisotropy, forming part of a family of particle-like magnetic objects, which may be excited for high-frequency applications. Here, the authors determine a current–field phase diagram for magnetic droplet nucleation.