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The interest in understanding scaling limits of magnetic textures such as domain walls spans the entire field of magnetism from its physical fundamentals to applications in information technologies. Here, we explore antiferromagnetic CuMnAs in which imaging by x-ray photoemission reveals the presence of magnetic textures down to nanoscale, reaching the detection limit of this established microscopy in antiferromagnets. We achieve atomic resolution by using differential phase-contrast imaging within aberration-corrected scanning transmission electron microscopy. We identify abrupt domain walls in the antiferromagnetic film corresponding to the Néel order reversal between two neighboring atomic planes. Our work stimulates research of magnetic textures at the ultimate atomic scale and sheds light on electrical and ultrafast optical antiferromagnetic devices with magnetic field-insensitive neuromorphic functionalities., This work was supported by the Ministry of Education of the Czech Republic grants LNSM-LNSpin and LM2018140, the Czech Science Foundation grant nos. 19-18623Y and 21-28876J, the University of Nottingham EPSRC Impact Acceleration Account grant no. EP/K503800/1, the EU FET Open RIA grant no. 766566, the Max Planck Partner Group grant, the Neuron Endowment Fund grant, and the National Grid Infrastructure MetaCentrum provided under the program “Projects of Large Research, Development, and Innovations Infrastructures” (CESNET LM2015042) and Innovations project IT4Innovations National Supercomputing Center–LM2015070. We also thank Diamond Light Source for the provision beam time under proposal number MM22437. The atomically resolved DPC-STEM experiments and the lamellae preparation were supported by the Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility, and also by the CzechNanoLab project LM2018110, CEITEC Nano Research Infrastructure. We acknowledge the Swedish Research Council, Carl Trygger’s foundation, and Olle Engkvist’s foundation for financial support. Multislice calculations were enabled by resources provided by the Swedish National Infrastructure for Computing (SNIC), partially funded by the Swedish Research Council through grant agreement no. 2018-05973. We also acknowledge MAX IV Laboratory for time on Beamline NanoMAX under proposal 20190533. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research Council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

This work deals with magneto-optical measurements using a recently built prototype of a two- dimensional electromagnet. In the first stage, an experimental setup for magneto-optical measurements was constructed, which enables to study Voigt effect and magnetic linear dichroism. In the second stage, this setup was tested by measuring hysteresis loops in a sample of ferromagnetic semiconductor GaMnAs. In the final stage, we performed a new type of magneto- optical experiments, which fully exploits the two-dimensional control of the magnetic field generated in the electromagnet.

In this thesis we studied precession mechanism in ferromagnetic thin film half-metal NiMnSb. We measured magnetization oscillations using optical pump and probe experiment at temperatures between 15 and 200 K and we evaluated the magnetic anisotropy fields, spin stiffness and Gilbert damping. New setup for ferromagnetic resonance measurement was built utilizing vector network analyser. With this setup we measured FMR at temperatures between 300 and 75 K. We evaluated the same parameters from FMR experiments as from the optical one. We found very good agreement in results obtained by the two methods. Powered by TCPDF (www.tcpdf.org)