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Seminarium Fizyki Ciała Stałego i Seminarium ACMiN: "Spin chirality in systems with broken inversion symmetry"
Środa, 5. Grudzień 2018, 09:00 - 11:00

Uprzejmie zapraszamy na Środowiskowe Seminarium Fizyki Ciała Stałego i Seminarium ACMiN, które odbędzie się w środę 5 grudnia 2018 r. o godz. 9.00 w Sali Audytoryjnej ACMiN AGH na II piętrze budynku D-16 (ul. Kawiory 30).

Referat pod tytułem "Spin chirality in systems with broken inversion symmetry" wygłosi Dr. inż. Piotr Kuświk (Institute of Molecular Physics, Polish Academy of Sciences, Poznań).


Nowadays, spin chirality is being widely investigated in magnetic materials because it suggest new approaches for material engineering, which can be suitable for application in high-density information storage and logic circuits. The most extensive studies are carried out for magnetic thin films with broken inversion symmetry, where the spin chirality is adjusted via the interfacial Dzyaloshinskii-Moriya interaction (iDMI) [1]. This interaction in systems with perpendicular magnetic anisotropy (PMA) may stabilize chiral Néel-type domain walls (walls with spin rotation in a plane perpendicular to the surface of the domain wall) or skyrmions (nanometer sized topological protected chiral spin configurations). Therefore, a lot of attention is paid to tune the strength and sign of iDMI, in particular in ferromagnetic(F)/heavy metal(HM) multilayers or HM/F/nonmagnetic oxide systems, where it was found that Néel domain walls or skyrmions can be moved with high speed by the electric current [2]. In light of recent result [3], it is known that skyrmions can be stabilized at room temperature by perpendicular exchange bias in HM/F/antiferromagnetic(AF) systems without any external magnetic field, which is an important step forward for skyrmion-based applications.
Therefore, here we focused our studies in Au(HM)/Co(F)/NiO(AF) layered systems, where we found that the NiO layer orients the magnetization of the Co layer perpendicularly to the sample plane due the exchange bias coupling between Co and NiO spins [4]. As a consequence, for Co layers covered with NiO the spin reorientation transition from out-of-plane to easy-plane occurs at much larger thicknesses than if the Co was covered with Au. Due to symmetry breaking of the Co interfaces, this system shows iDMI and the use of antiferromagnetic layers allows to obtain significant perpendicular exchange bias field [5, 6]. Using polar magneto-optical Kerr effect measurements we showed that in such system the Néel domain walls with clockwise chirality are stabilized by a strong negative iDMI [5], which is independent of the direction of perpendicular exchange bias coupling [6]. Additionally, we demonstrated that due to this spin configuration in DWs the domain propagation can be controlled with high precision by homogeneous external magnetic fields simultaneously applied out-of-plane and in-plan [5]. This concept can be attractive for many applications based on field-induced domain motion.

[1] A. Fert et al., Nature Materials 2, 17031 (2017)
[2] A. Fert et al., Nature Nanotechnology 8, 152 (2013)
[3] G. Yu, et al., Nano Lett. 18, 980 (2018)
[4] P. Kuświk et al., J. Appl. Phys. 119, 215307 (2016)
[5] P. Kuświk et al., Phys. Rev. B 97, 024404 (2018)
[6] P. Kuświk et al., J. Mag. Mag. Mat.472, 29 (2019)

Miejsce : Sala Audytoryjna ACMiN AGH (1.02A), na II piętrze pawilonu D-16 (ul. Kawiory 30)