Seminar – Magneto-thermo-transport phenomena in antiferromagnets with non-collinear spin structure

On Friday, September 17th at 11:00Eva Schmoranzerova, research scientist at Faculty of Mathematics and Physics, Charles University, Prague will give us a seminar entitled:
Magneto-thermo-transport phenomena in antiferromagnets with non-collinear spin structure

Place : CEA Bat. 10.05 Room 445 (limited to 30 persons having a CEA Badge)
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Non-collinear antiferromagnets (NC-AFMs), new materials with non-collinear spin structure, offer a significant potential for spintronic applications [1]. They have vanishingly small magnetization and ultrafast spin dynamics. In addition, they allow for important counterparts to the effects considered to be exclusive to materials with net magnetization, such as the anomalous Hall effect (AHE) [2], magneto-optical Kerr effect [3] or anomalous Nernst effect (ANE) [4].
In this talk we are going to present our latest experiments in thermo-magneto-transport on epitaxial thin films of non-collinear antiferromagnets, with the emphasis on observation of the anomalous Nernst and Hall effect. The work is part of the MATHEEIAS (ANR-DFG) project. We will focus on two systems, kagome-lattice antiferromagnet Mn3NiN and multi-sublattice antiferromagnet Mn5Si3. Both the systems share certain similarities in relatively weak spin orbit coupling, where the magneto- and thermo-transport effects originate in Berry phase curvature of the band structure. However, while Mn3NiN is non-collinear in its low temperature AFM phase and ferrimagnetic above its Neel temperature for compressively strained films [5] , the Mn5Si3 changes its spin structure from the NC-AFM at low temperatures to collinear AFM at temperatures above roughly 90 K. The latter material belongs to the newly emerging class of “alter-magnets”, which display strong spontaneous Hall effect resulting solely from the Zeeman splitting [6,7].
We will show our results on magneto -thermo-transport obtained using two complementary methods. First, the global thermo-transport response is measured using a micro-patterned Hall bar device with platinum resistive heaters, inducing an in-plane thermal gradient. In addition, standard magneto-transport can be measured simultaneously within the same experiment. To add spatial resolution to the thermo-transport, the scanning thermal gradient microscopy [4] was used. A laser beam incident on micro-patterned device induces local thermal gradients, which enables to reveal domain structure of the particular material. By comparison of these methods, it is possible to quantify the size of the observed thermo-transport effects and to study their relation to the magneto-transport response.
[1] J. Železný, Y. Zhang, C. Felser, and B. Yan, Phys. Rev. Lett. 119, 187204 (2017).
[2] Nakatsuji, S., Kiyohara, N. & Higo, Nature 527, 212–215 (2015).
[3] T. Higo, et al. Nature Photon. 12, 73–78 (2018).
[4] H. Reichlová et al., Nat. Commun. 10, 5459 (2019).
[5] D. Boldrin et al., Phys. Rev. Materials 3, 094409 (2019).
[6] L. Šmejkal, J. Sinova, and T. Jungwirth: arXiv:2105.05820, 2021.
[7] H. Reichlova et al.: arXiv:2012.15651, 2020


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