Terahertz inverse spin Hall effect in spintronic nanostructures with various ferromagnetic materials
Journal Article
·
· Journal of Magnetism and Magnetic Materials
- University of Rochester, NY (United States); Laboratory for Laser Energetics, University of Rochester
- University of Rochester, NY (United States)
- Peter Grünberg Institute, Jülich (Germany)
- Peter Grünberg Institute, Jülich (Germany); University Duisburg-Essen (Germany)
- Peter Grünberg Institute, Jülich (Germany); Qingdao University (China)
- Research Centre Jülich (Germany)
- Peter Grünberg Institute, Jülich (Germany); University of California Davis, CA (United States)
- Polish Academy of Sciences, Warszawa (Poland)
Bilayers of ferromagnetic and heavy metal nanolayers excited with femtosecond laser pulses emit subpicosecond bursts of electromagnetic radiation with spectral frequencies up to several THz. We fabricated such spintronic THz emitters containing various ferromagnetic materials with vastly different magnetic remanence, saturation magnetization, and coercive fields. In all cases, the THz amplitude versus magnetic-field dependence follows the independently measured magnetization hysteresis loops and the THz polarization direction is perpendicular to the sample’s magnetization M, both consistent with the inverse spin Hall effect (ISHE) as the physical origin. The mV-level signals of observed THz transient also favor the ISHE over the anomalous Nernst effect (ANE). The M(T) variation governs the temperature dependence of the THz generation. Emitters with weakly remanent ferromagnets are magnetic-field tunable, while moderately and strongly remanent ferromagnets, once magnetized, allow intense THz generation even without an external field, nevertheless exhibiting low susceptibility to magnetic perturbations if the hysteresis loop is square. Hence, exploiting the magnetic properties of the ferromagnetic layer enables tailoring of weakly temperature-dependent spintronic THz emitters. Finally, we explored the applicability of perovskite oxide materials such as La-Sr-Mn-O (LSMO) for THz transient generation. We detected weak (<40-μV amplitude) THz emissions from both LSMO/Au and pure LSMO nanostructures with no sign flip upon the sample reversal. Furthermore, we excluded the ISHE and believe it was likely governed by the ANE in the thick-film regime, although we cannot exclude the transient demagnetization mechanism.
- Research Organization:
- University of Rochester, NY (United States)
- Sponsoring Organization:
- USDOE; USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- NA0004144; SC0021468
- OSTI ID:
- 2324788
- Alternate ID(s):
- OSTI ID: 2369910
- Journal Information:
- Journal of Magnetism and Magnetic Materials, Journal Name: Journal of Magnetism and Magnetic Materials Vol. 593; ISSN 0304-8853
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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