ONLINE - nanoGUNE Colloquium: Antiferromagnetic Insulatronics: Spintronics without magnetic fields
CIC nanoGUNE Seminars
- Speaker
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Mathias Kläui; Institute of Physics, Johannes Gutenberg-University Mainz
- When
-
2020/11/09
12:00 - Place
- nanoGUNE online Webinar
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**Antiferromagnetic Insulatronics: Spintronics without magnetic fields**
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Mathias Kläui1,2,3,*
1Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz,
Germany
2Graduate School of Excellence Materials Science in Mainz, 55128 Mainz,
Germany
3Centre for Quantum Spintronics, NTNU, 7034 Trondheim, Norway
*IEEE Magnetics Society Distinguished Lecturer
[Klaeui@uni-mainz.de](mailto:Klaeui@uni-mainz.de)
While known for a long time, antiferromagnetically ordered systems have
previously been considered, as expressed by Louis Néel in his Nobel Prize
Lecture, to be “interesting but uselessâ€. However, since antiferromagnets
potentially promises faster operation, enhanced stability with respect to
interfering magnetic fields and higher integration due to the absence of
dipolar coupling, they could potentially become a game changer for new
spintronic devices. The zero net moment makes manipulation using conventional
magnetic fields challenging. However recently, these materials have received
renewed attention due to possible manipulation based on new approaches such as
photons [1] or spin-orbit torques [2].
In this talk, we will present an overview of the key features of
antiferromagnets to potentially functionalize their unique properties. This
includes writing, reading and transporting information using antiferromagnets.
We recently realized switching in the metallic antiferromagnet Mn2Au by
intrinsic staggered spin-orbit torques [3,4] and characterize the switching
properties by direct imaging. While switching by staggered intrinsic spin-
orbit torques in metallic AFMs requires special structural asymmetry,
interfacial non-staggered spin-orbit torques can switch multilayers of many
insulating AFMs capped with heavy metal layers.
We probe switching and spin transport in selected collinear insulating
antiferromagnets, such as NiO [5-7], CoO [8,9] and hematite [10,11]. In NiO
and CoO we find that there are multiple switching mechanisms that result in
the reorientation of the Néel vector and additionally effects related to
electromigration of the heavy metal layer can obscure the magnetic switching
[5,7,9]. For the spin transport, spin currents are generated by heating as
resulting from the spin Seebeck effect and by spin pumping measurements and we
find in vertical transport short (few nm) spin diffusion lengths [6,8].
For hematite, however, we find in a non-local geometry that spin transport of
tens of micrometers is possible [10,11]. We detect a first harmonic signal,
related to the spin conductance, that exhibits a maximum at the spin-flop
reorientation, while the second harmonic signal, related to the Spin Seebeck
conductance, is linear in the amplitude of the applied magnetic field [10].
The first signal is dependent on the direction of the Néel vector and the
second one depends on the induced magnetic moment due to the field. We
identify the domain structure as the limiting factor for the spin transport
[11]. We recently also achieved transport in the easy plane phase [12], which
allows us to obtain long distance spin transport in hematite even at room
temperature [12]. From the power and distance dependence, we unambiguously
distinguish long-distance transport based on diffusion [10,11] from predicted
spin superfluidity that can potentially be used for logic [13].
A number of excellent reviews are available for further information on recent
developments in the field [14].
**References **
[1] A. Kimel et al., Nature **429** , 850 (2004).
[2] J. Zelezny et al., Phys. Rev. Lett. **113** , 157201 (2014); P. Wadley et
al., Science **351** , 587 (2016).
[3] S. Bodnar et al., Nature Commun. **9** , 348 (2018)
[4] S. Bodnar et al., Phys. Rev. B **99** , 140409(R) (2019).
[5] L. Baldrati et al., Phys. Rev. Lett. **123** , 177201 (2019)
[6] L. Baldrati et al., Phys. Rev. B **98** , 024422 (2018); L. Baldrati et
al. Phys. Rev. B **98** , 014409 (2018)
[7] F. Schreiber et al., Appl. Phys. Lett. **117** , 082401 (2020)
[8] J. Cramer et al., Nature Commun. **9** , 1089 (2018)
[9] L. Baldrati et al., Phys. Rev. Lett. **125** , 077201 (2020)
[10] R. Lebrun et al., Nature **561** , 222 (2018).
[11] A. Ross et al., Nano Lett. **20** , 306 (2020).
[12] R. Lebrun et al., arxiv:2005.14414 (2020) (Nature Comms. in press).
[13] Y. Tserkovnyak et al., Phys. Rev. Lett. **119** , 187705 (2017).
[14] Rev. Mod. Phys. 90, 15005 (2018); Nat. Phys. 14, 200-242 (2018); Adv.
Mater. 32, 1905603 (2020)
**Host:** A. Berger
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ONLINE nanoGUNE Colloquium: Mathias Kläui; University of Mainz - CIC nanoGUNE
When: Nov 9, 2020 11:00 AM Madrid
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