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Magnetooptical observations of thin magnetic cylinders: theory and experiment (K. Richter1*, O. Vahovsky3, A. Thiaville2, R. Varga3 and J. McCord1) 1 University of Kiel, Kaiserstraße 2, 24143 Kiel, Germany 2University Paris Sud XI, 914 00, Orsay, France 3 University of Pavol Jozef Safarik, 040 01 Kosice, Slovakia *e-mail: kornel.richter@gmail.com Thin cylindrical wires attract considerable attention due to the interesting features of domain wall motion like absence of the Walker breakdown that prevents very high domain wall velocities [1]. While several experimental techniques allow for well controllable deposition of magnetic structures with complex geometries [2], a reliable determination of the surface magnetization usually meets several obstacles in case of samples with curved surface. Here, we provide a full analytical calculation of the Magneto-Optical Kerr Effect (MOKE) contrast for cylinders with reduced diameter. It is shown that the cylindrical shape of sample surface gives rise to a spatial distribution of the planes of incidence that are all tilted each to other [3]. Such mutual orientation of incident rays in combination with circumferential dependence of a local angle of incidence gives rise to apparent magneto-optical contrasts [3,4] that cannot be interpreted well without considering the curved surface of a cylinder. Theoretical calculations [3] are tested experimentally on amorphous glass-coated microwires with well-defined cylindrical shape. Finally, we use our framework to study shape of the domain wall in FeSiB microwire characterized by very fast domain wall propagation. The setup is optimized for characteristic optical and magneto-optical features of thin magnetic cylinders. Time-resolved measurements of a magnetic contrast along the circumference of wire are used to reconstruct a three-dimensional image of a surface domain wall shape. Our measurements confirm a tilted shape of domain wall [5, 6], in agreement with previous observations of microwires with positive magnetostriction alloy. The experimental technique represents a new way for direct visualizations of a surface magnetism of thin cylinders in optical range. [1] M. Yan, et al., Phys. Rev. Lett. 104, 057201 (2010). [2] A. Fernández-Pacheco, et al., Sci. Rep. 3, 1492 (2013). [3] K. Richter, et al., Phys. Rev.B 96, 064421 (2017). [4] K. Richter, et al., IEEE Trans. Magn. 50, 2501404 (2014). [5] K. Richter, et al., J. Appl. Phys.127, 193305 (2020). [6] O. Vahovsky, et al., J. Magn. Magn. Mater. 483, 266 (2019).

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Kornel Richter, University of Kiel
Zoom: https://uni-koeln.zoom.us/j/96710889575?pwd=MjVKdkk1dnZKazBvVkdTdk5TTHZyUT09
Contact: Ionela Lindfors-Vrejoiu