Abstract-Néel Spin-Orbit Torque Driven Antiferromagnetic Resonance in Mn 2 Au Probed by Time-Domain THz Spectroscopy

N. Bhattacharjee, A. A. Sapozhnik, S. Yu. Bodnar, V. Yu. Grigorev, S. Y. Agustsson, J. Cao, D. Dominko, M. Obergfell, O. Gomonay, J. Sinova, M. Kläui, H.-J. Elmers, M. Jourdan, and J. Demsar

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.237201

We observe the excitation of collective modes in the terahertz (THz) range driven by the recently discovered Néel spin-orbit torques (NSOTs) in the metallic antiferromagnet ${\mathrm{Mn}}_2\mathrm{Au}$. Temperature-dependent THz spectroscopy reveals a strong absorption mode centered near 1 THz, which upon heating from 4 to 450 K softens and loses intensity. A comparison with the estimated eigenmode frequencies implies that the observed mode is an in-plane antiferromagnetic resonance (AFMR). The AFMR absorption strength exceeds those found in antiferromagnetic insulators, driven by the magnetic field of the THz radiation, by 3 orders of magnitude. Based on this and the agreement with our theory modeling, we infer that the driving mechanism for the observed mode is the current-induced NSOT. Here the electric field component of the THz pulse drives an ac current in the metal, which subsequently drives the AFMR. This electric manipulation of the Néel order parameter at high frequencies makes ${\mathrm{Mn}}_2\mathrm{Au}$ a prime candidate for antiferromagnetic ultrafast memory applications.

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Abstract-N\'{e}el spin orbit torque driven antiferromagnetic resonance in Mn 2 Au probed by time-domain THz spectroscopy

N. Bhattacharjee, A. A. Sapozhnik, S. Yu. Bodnar, V. Yu. Grigorev, S. Y. Agustsson, J. Cao, D. Dominko, M. Obergfell, O. Gomonay, J. Sinova, M. Kläui, H. -J. Elmers, M. Jourdan, and J. Demsar

https://journals.aps.org/prl/accepted/32071Y5cC871765f240317f6796a5ec9679dbb0ac

We observe the excitation of collective modes in the THz range driven by the recently discovered N\'{e}el spin-orbit torques (NSOT) in the metallic antiferromagnet Mn${}_2$Au. Temperature dependent THz spectroscopy reveals a strong absorption mode centered near 1 THz, which upon heating from 4 K to 450 K softens and looses intensity. Comparison with the estimated eigenmode frequencies implies that the observed mode is an in-plane antiferromagnetic resonance (AFMR). The AFMR absorption strength exceeds those found in antiferromagnetic insulators, driven by the magnetic field of the THz radiation, by three orders of magnitude. Based on this and the agreement with our theory modelling, we infer that the driving mechanism for the observed mode is the current induced NSOT. Here the electric field component of the THz pulse drives an AC current in the metal, which subsequently drives the AFMR. This electric manipulation of the N\'{e}el order parameter at high frequencies makes Mn${}_2$Au a prime candidate for AFM ultrafast memory applications.

Abstract-Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

• T. Seifert,
• S. Jaiswal,
• U. Martens,
• J. Hannegan,
• L. Braun,
• P. Maldonado,
• F. Freimuth,
• A. Kronenberg,
• J. Henrizi,
• I. Radu,
• E. Beaurepaire,
• Y. Mokrousov,
• P. M. Oppeneer,
• M. Jourdan,
• G. Jakob,
• D. Turchinovich,
• L. M. Hayden,
• M. Wolf,
• M. Münzenberg,
• M. Kläui
• & T. Kampfrath
• • http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2016.91.html

Terahertz electromagnetic radiation is extremely useful for numerous applications, including imaging and spectroscopy. It is thus highly desirable to have an efficient table-top emitter covering the 1–30 THz window that is driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source that relies on three tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photoinduced spin currents, the inverse spin-Hall effect and a broadband Fabry–Pérot resonance. Guided by an analytical model, this spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1–30 THz range. Our novel source outperforms laser-oscillator-driven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz field amplitude, flexibility, scalability and cost.

Abstract-Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

T. Seifert,

S. Jaiswal,

U. Martens,

J. Hannegan,

L. Braun,

P. Maldonado,

F. Freimuth,

A. Kronenberg,

J. Henrizi,

I. Radu,

E. Beaurepaire,

Y. Mokrousov,

P. M. Oppeneer,

M. Jourdan,

G. Jakob,

D. Turchinovich,

L. M. Hayden,

M. Wolf,

M. Münzenberg,

M. Kläui

& T. Kampfrath 

(some author names deleted from Labels at the bottom due to blogger word limit)

http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2016.91.html

Terahertz electromagnetic radiation is extremely useful for numerous applications, including imaging and spectroscopy. It is thus highly desirable to have an efficient table-top emitter covering the 1–30 THz window that is driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source that relies on three tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photoinduced spin currents, the inverse spin-Hall effect and a broadband Fabry–Pérot resonance. Guided by an analytical model, this spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1–30 THz range. Our novel source outperforms laser-oscillator-driven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz field amplitude, flexibility, scalability and cost.

Abstract-Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

T. Seifert, S. Jaiswal, U. Martens, J. Hannegan, L. Braun, P. Maldonado, F. Freimuth, A. Kronenberg, J. Henrizi, I. Radu, E. Beaurepaire, Y. Mokrousov, P. M. Oppeneer, M. Jourdan, G. Jakob,D. Turchinovich, L. M. Hayden, M. Wolf, M. Münzenberg, M. Kläui, T. Kampfrath

http://www.mathpubs.com/detail/1510.03729v1/Efficient-metallic-spintronic-emitters-of-ultrabroadband-terahertz-radiation

Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source based on tailored fundamental spintronic/photonic phenomena in magnetic metal multilayers: a spin-dependent generalization of the photo-Dember effect, the inverse spin-Hall effect and a broadband Fabry-P\'erot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort THz pulses fully covering the 1-to-30-THz range. Our novel source outperforms standard emitters such as ZnTe(110) crystals in terms of bandwidth, conversion efficiency, flexibility, scalability and cost.