8.7 Conclusion
199
where as spin current is detected through the ISHE, which transforms a spin current
into a transverse charge current in materials with strong spin–orbit interaction. The
unanswered fundamental problem in spintronic is the electrical writing speed limit,
which is in the GHz range. Terahertz writing speed is a realistic prospect in CuMnAs
and can open the door of an ultrafast complete write–read cycle in antiferromagnetic memories. The ultrafast writing of antiferromagnetic bit cells can possibly be
explored without separate THz speed processors.
8.8 Exercises
Q.1. What is TeraHertz radiation? Give some examples of scientific phenomena
observed in picosecond scale (THz frequency range).
Q.2. Explain the importance of THz radiation in science and technology. Why do
we need THz spintronics?
Q.3. Mention the observations that lead to the implementation of spin-dependent
phenomena in THz scale.
Q.4. What are different types of THz emitters? Explain the basic principle of
operation of metallic spintronic THz emitter.
Q.5. Explain the criteria for the selection of material towards implementation of
THz emitter. Compare the performances between metallic magnet (Fe) and
non-metallic magnet (YIG) in THz emitter.
Q.6. Discuss the role of complex magnetic compounds in terahertz emission.
Q.7. What do you mean by THz writing scheme? How can it be implemented in
spintronics?
References
L. Bocklage, Coherent THz transient spin currents by spin pumping. Phys. Rev. Lett. 118, 257202
(2017)
K.J. Chau, A.Y. Elezzabi, Photonic anisotropic magnetoresistance in dense Co particle ensembles.
Phys. Rev. Lett. 96, 033903 (2006)
F. Freimuth, S. Blügel, Y. Mokrousov, Direct and inverse spin-orbit torques. Phys. Rev. B. 92,
064415 (2015)
S.D. Ganichev, E.L. Ivchenko, V.V. Bel’Kov et al., Spin-galvanic effect. Nature 417, 153–156 (2002)
R.I. Herapath, S.M. Hornett, T.S. Seifert et al., Impact of pump wavelength on terahertz emission
of a cavity-enhanced spintronic trilayer. Appl. Phys. Lett. 114, 041107 (2019)
T. Kampfrath, Probing and controlling spin dynamics with THz pulses (2018). https://magnetism.
eu/esm/2018/slides/kampfrath-slides.pdf
T. Kampfrath, M. Battiato, P. Maldonado et al., Terahertz spin current pulses controlled by magnetic
heterostructures. Nat. Nanotechnol. 8, 256–260 (2013)
A.V. Kimel, A. Kirilyuk, P.A. Usachev et al., Ultrafast non-thermal control of magnetization by
instantaneous photomagnetic pulses. Nature 435, 655–657 (2005)
Y.S. Lee, Principles of terahertz science. Springer Publication. ISBN 978-0-387-09539-4 (2009)
199
where as spin current is detected through the ISHE, which transforms a spin current
into a transverse charge current in materials with strong spin–orbit interaction. The
unanswered fundamental problem in spintronic is the electrical writing speed limit,
which is in the GHz range. Terahertz writing speed is a realistic prospect in CuMnAs
and can open the door of an ultrafast complete write–read cycle in antiferromagnetic memories. The ultrafast writing of antiferromagnetic bit cells can possibly be
explored without separate THz speed processors.
8.8 Exercises
Q.1. What is TeraHertz radiation? Give some examples of scientific phenomena
observed in picosecond scale (THz frequency range).
Q.2. Explain the importance of THz radiation in science and technology. Why do
we need THz spintronics?
Q.3. Mention the observations that lead to the implementation of spin-dependent
phenomena in THz scale.
Q.4. What are different types of THz emitters? Explain the basic principle of
operation of metallic spintronic THz emitter.
Q.5. Explain the criteria for the selection of material towards implementation of
THz emitter. Compare the performances between metallic magnet (Fe) and
non-metallic magnet (YIG) in THz emitter.
Q.6. Discuss the role of complex magnetic compounds in terahertz emission.
Q.7. What do you mean by THz writing scheme? How can it be implemented in
spintronics?
References
L. Bocklage, Coherent THz transient spin currents by spin pumping. Phys. Rev. Lett. 118, 257202
(2017)
K.J. Chau, A.Y. Elezzabi, Photonic anisotropic magnetoresistance in dense Co particle ensembles.
Phys. Rev. Lett. 96, 033903 (2006)
F. Freimuth, S. Blügel, Y. Mokrousov, Direct and inverse spin-orbit torques. Phys. Rev. B. 92,
064415 (2015)
S.D. Ganichev, E.L. Ivchenko, V.V. Bel’Kov et al., Spin-galvanic effect. Nature 417, 153–156 (2002)
R.I. Herapath, S.M. Hornett, T.S. Seifert et al., Impact of pump wavelength on terahertz emission
of a cavity-enhanced spintronic trilayer. Appl. Phys. Lett. 114, 041107 (2019)
T. Kampfrath, Probing and controlling spin dynamics with THz pulses (2018). https://magnetism.
eu/esm/2018/slides/kampfrath-slides.pdf
T. Kampfrath, M. Battiato, P. Maldonado et al., Terahertz spin current pulses controlled by magnetic
heterostructures. Nat. Nanotechnol. 8, 256–260 (2013)
A.V. Kimel, A. Kirilyuk, P.A. Usachev et al., Ultrafast non-thermal control of magnetization by
instantaneous photomagnetic pulses. Nature 435, 655–657 (2005)
Y.S. Lee, Principles of terahertz science. Springer Publication. ISBN 978-0-387-09539-4 (2009)