158
R. Mattana et al.
(for both polarities) and is probably pinned by a material defect. Skyrmion velocities
can be extracted [see Fig. 5.18f] and it is shown that they increase from ∼50 m s
−1
to ∼120 m s
−1 by replacing Co by CoFeB. These measurements allow to conclude
that lower pinning materials such as amorphous CoFeB layer, i.e. without grain
boundaries, are probably more appropriate to get an efficient skyrmion motion.
X-ray microscopy is thus a powerful tool to study in real time the current-driven
magnetization dynamics in various magnetic systems. We have shown three examples where magnetic reversal, domain walls and skyrmion motion are investigated
by STXM or XMCD-PEEM. This is not limited to FM systems as antiferromagnetic
domains can be also probed by performing linear dichroism. Recently, M. J. Grzybowski et al. have measured current-induced antiferromagnetic domain switching in
CuMnAs by performing XMLD-PEEM measurements [64].
5.3 Conclusion
We have shown through few examples that synchrotron radiation-based spectroscopies are powerful techniques to perform advanced characterization of various
spintronic systems. For example, XAS (including circular and linear dichroism)
allows probing the electronic and magnetic properties of surfaces, interfaces and
bulk materials. Spin- and angle-resolved photoemission is an ideal tool to measure
the actual spin polarization and reveal the density of states of surfaces and interfaces. It can be applied to a wide variety of materials used in spintronic devices
such as ferromagnets, antiferromagnets, topological insulators, Rashba interfaces,
hybrid ferromagnet/molecules interfaces, 2D materials and multiferroics. XPEEM
and STXM are also perfect techniques to study the dynamics of magnetic structures
(ferromagnetic, ferrimagnetic and antiferromagnetic) but also to measure locally
the electronic structure of surfaces. This is not exhaustive; other techniques such
as X-ray magnetic scattering, resonant inelastic X-ray scattering, hard X-ray photoelectron spectroscopy, nano-ARPES can be also used to probe spintronic device
properties. Finally, the development of new techniques such as magnetic X-ray nanotomography [65] and novel X-ray sources (new generation of synchrotron and Xray free-electron lasers) improving coherence, spatial and temporal resolution, will
allow obtaining deeper characterization and understanding of magnetic textures and
spintronic devices.
Acknowledgements Financial support from the Agence Nationale de la Recherche, France, under
grant agreement No. ANR-17-CE24-0025 (TOPSKY), the DARPA TEE program, through grant
MIPR No. HR0011831554 and the Horizon2020 Framework Programme of the European Commission, under FET-Proactive Grant agreement No. 824123 (SKYTOP), is acknowledged.
R. Mattana et al.
(for both polarities) and is probably pinned by a material defect. Skyrmion velocities
can be extracted [see Fig. 5.18f] and it is shown that they increase from ∼50 m s
−1
to ∼120 m s
−1 by replacing Co by CoFeB. These measurements allow to conclude
that lower pinning materials such as amorphous CoFeB layer, i.e. without grain
boundaries, are probably more appropriate to get an efficient skyrmion motion.
X-ray microscopy is thus a powerful tool to study in real time the current-driven
magnetization dynamics in various magnetic systems. We have shown three examples where magnetic reversal, domain walls and skyrmion motion are investigated
by STXM or XMCD-PEEM. This is not limited to FM systems as antiferromagnetic
domains can be also probed by performing linear dichroism. Recently, M. J. Grzybowski et al. have measured current-induced antiferromagnetic domain switching in
CuMnAs by performing XMLD-PEEM measurements [64].
5.3 Conclusion
We have shown through few examples that synchrotron radiation-based spectroscopies are powerful techniques to perform advanced characterization of various
spintronic systems. For example, XAS (including circular and linear dichroism)
allows probing the electronic and magnetic properties of surfaces, interfaces and
bulk materials. Spin- and angle-resolved photoemission is an ideal tool to measure
the actual spin polarization and reveal the density of states of surfaces and interfaces. It can be applied to a wide variety of materials used in spintronic devices
such as ferromagnets, antiferromagnets, topological insulators, Rashba interfaces,
hybrid ferromagnet/molecules interfaces, 2D materials and multiferroics. XPEEM
and STXM are also perfect techniques to study the dynamics of magnetic structures
(ferromagnetic, ferrimagnetic and antiferromagnetic) but also to measure locally
the electronic structure of surfaces. This is not exhaustive; other techniques such
as X-ray magnetic scattering, resonant inelastic X-ray scattering, hard X-ray photoelectron spectroscopy, nano-ARPES can be also used to probe spintronic device
properties. Finally, the development of new techniques such as magnetic X-ray nanotomography [65] and novel X-ray sources (new generation of synchrotron and Xray free-electron lasers) improving coherence, spatial and temporal resolution, will
allow obtaining deeper characterization and understanding of magnetic textures and
spintronic devices.
Acknowledgements Financial support from the Agence Nationale de la Recherche, France, under
grant agreement No. ANR-17-CE24-0025 (TOPSKY), the DARPA TEE program, through grant
MIPR No. HR0011831554 and the Horizon2020 Framework Programme of the European Commission, under FET-Proactive Grant agreement No. 824123 (SKYTOP), is acknowledged.