--- _id: '1426' abstract: - lang: eng text: Round magnetic nano-dots belong to the frequently investigated magnetic nanostructures since they can often reverse magnetization via a vortex state which is characterized by low stray fields, making them useful for data storage applications. Nano-rings, with an open aperture in the middle, regularly show flux-closed vortex states without a vortex core, again reducing stray fields. Here we theoretically investigate “Pac-Man” shaped iron nanostructures with varying aperture, i.e. structures ranging from a thin ring to a solid cylinder with a triangular cut. Our results show that in most cases, a vortex-like state without vortex core along the whole nanostructure occurs during magnetization reversal. Depending on the angle of the external magnetic field and the nanostructure thickness, different magnetization reversal processes have been found, including domain wall nucleation and propagation as well as small vortex states with cores. The occurrence of such special magnetic states can be attributed to the interaction of the shape anisotropy with the relatively high magneto-crystalline anisotropy of iron. Our simulations reveal the possibilities to use such structures for data storage applications as well as their importance in basic research, enabling formation of asymmetric magnetic structures beyond common onion and symmetric vortex states. article_number: '168205' article_type: original author: - first_name: Fatima-Zohra full_name: Bachar, Fatima-Zohra last_name: Bachar - first_name: Christian full_name: Schröder, Christian id: '35809' last_name: Schröder orcid: 0000-0002-6391-6548 orcid_put_code_url: https://api.orcid.org/v2.0/0000-0002-6391-6548/work/96660667 - first_name: Andrea full_name: Ehrmann, Andrea id: '223776' last_name: Ehrmann orcid: 0000-0003-0695-3905 orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/96660668 citation: alphadin: 'Bachar, Fatima-Zohra ; Schröder, Christian ; Ehrmann, Andrea: Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture. In: Journal of Magnetism and Magnetic Materials Bd. 537, Elsevier BV (2021)' ama: Bachar F-Z, Schröder C, Ehrmann A. Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture. Journal of Magnetism and Magnetic Materials. 2021;537. doi:10.1016/j.jmmm.2021.168205 apa: Bachar, F.-Z., Schröder, C., & Ehrmann, A. (2021). Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture. Journal of Magnetism and Magnetic Materials, 537. https://doi.org/10.1016/j.jmmm.2021.168205 bibtex: '@article{Bachar_Schröder_Ehrmann_2021, title={Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture}, volume={537}, DOI={10.1016/j.jmmm.2021.168205}, number={168205}, journal={Journal of Magnetism and Magnetic Materials}, publisher={Elsevier BV}, author={Bachar, Fatima-Zohra and Schröder, Christian and Ehrmann, Andrea}, year={2021} }' chicago: Bachar, Fatima-Zohra, Christian Schröder, and Andrea Ehrmann. “Magnetization Reversal in Pac-Man Shaped Fe Nanostructures with Varying Aperture.” Journal of Magnetism and Magnetic Materials 537 (2021). https://doi.org/10.1016/j.jmmm.2021.168205. ieee: F.-Z. Bachar, C. Schröder, and A. Ehrmann, “Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture,” Journal of Magnetism and Magnetic Materials, vol. 537, 2021. mla: Bachar, Fatima-Zohra, et al. “Magnetization Reversal in Pac-Man Shaped Fe Nanostructures with Varying Aperture.” Journal of Magnetism and Magnetic Materials, vol. 537, 168205, Elsevier BV, 2021, doi:10.1016/j.jmmm.2021.168205. short: F.-Z. Bachar, C. Schröder, A. Ehrmann, Journal of Magnetism and Magnetic Materials 537 (2021). date_created: 2021-07-06T09:07:19Z date_updated: 2023-03-08T09:29:40Z doi: 10.1016/j.jmmm.2021.168205 intvolume: ' 537' keyword: - Magnetic nanostructures Micromagnetic simulation Magnetization reversal Iron Vortex state Domain walls Shape anisotropy language: - iso: eng main_file_link: - url: https://doi.org/10.1016/j.jmmm.2021.168205 project: - _id: f89a05bb-bcea-11ed-9442-ed382659bc06 name: Bielefelder Institut für Angewandte Materialforschung publication: Journal of Magnetism and Magnetic Materials publication_identifier: issn: - '03048853' publication_status: published publisher: Elsevier BV quality_controlled: '1' status: public title: Magnetization reversal in Pac-Man shaped Fe nanostructures with varying aperture type: journal_article user_id: '35809' volume: 537 year: '2021' ... --- _id: '1603' abstract: - lang: eng text: " Magnetic nanodots are of high interest for basic research due to their broad spectrum of possible magnetic states and magnetization reversal processes. Besides, they are of technological interest since they can be applied in magnetic data storage, especially if vortex states occur in closed dots or open rings. While producing such nanorings and nanodots from diverse magnetic materials by lithographic techniques is quite common nowadays, these production technologies are naturally prone to small deviations of the borders of these nanoparticles. Here we investigate the influence of well-defined angular-dependent roughness of the edges, created by building the nanoparticles from small cubes, on the resulting hysteresis loops and magnetization reversal processes in five different round nanodots with varying open areas, from a thin ring to a closed nanodot. By varying the orientation of the external magnetic field, the impact of the angle-dependent roughness can be estimated. Especially for the thinnest ring, significant dependence of the transverse magnetization component on the field orientation can be found.\r\n \ " article_number: '19' article_type: original author: - first_name: Pia full_name: Steinmetz, Pia last_name: Steinmetz - first_name: Andrea full_name: Ehrmann, Andrea id: '223776' last_name: Ehrmann orcid: 0000-0003-0695-3905 orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/105572063 citation: alphadin: 'Steinmetz, Pia ; Ehrmann, Andrea: Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry. In: Condensed Matter Bd. 6, MDPI AG (2021), Nr. 2' ama: Steinmetz P, Ehrmann A. Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry. Condensed Matter. 2021;6(2). doi:10.3390/condmat6020019 apa: Steinmetz, P., & Ehrmann, A. (2021). Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry. Condensed Matter, 6(2). https://doi.org/10.3390/condmat6020019 bibtex: '@article{Steinmetz_Ehrmann_2021, title={Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry}, volume={6}, DOI={10.3390/condmat6020019}, number={219}, journal={Condensed Matter}, publisher={MDPI AG}, author={Steinmetz, Pia and Ehrmann, Andrea}, year={2021} }' chicago: Steinmetz, Pia, and Andrea Ehrmann. “Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry.” Condensed Matter 6, no. 2 (2021). https://doi.org/10.3390/condmat6020019. ieee: P. Steinmetz and A. Ehrmann, “Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry,” Condensed Matter, vol. 6, no. 2, 2021. mla: Steinmetz, Pia, and Andrea Ehrmann. “Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry.” Condensed Matter, vol. 6, no. 2, 19, MDPI AG, 2021, doi:10.3390/condmat6020019. short: P. Steinmetz, A. Ehrmann, Condensed Matter 6 (2021). date_created: 2022-01-01T14:13:48Z date_updated: 2022-01-01T15:08:21Z department: - _id: '103' doi: 10.3390/condmat6020019 intvolume: ' 6' issue: '2' keyword: - OOMMF (Object Orientated MicroMagnetic Framework) - nanostructure - iron - vortex state - domain wall - rough borders language: - iso: eng license: https://creativecommons.org/licenses/by/4.0/ main_file_link: - open_access: '1' url: https://doi.org/10.3390/condmat6020019 oa: '1' publication: Condensed Matter publication_identifier: eissn: - 2410-3896 publication_status: published publisher: MDPI AG quality_controlled: '1' status: public title: Micromagnetic Simulation of Round Ferromagnetic Nanodots with Varying Roughness and Symmetry tmp: image: /images/cc_by.png legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0) short: CC BY (4.0) type: journal_article user_id: '223776' volume: 6 year: '2021' ... --- _id: '1616' abstract: - lang: eng text: Electrospun nanofibers produced from magnetic materials form a magnetic network which may be used for neuromorphic computing and other novel applications. While the influence of bending radii on the magnetization reversal in such nanofibers was already discussed in the literature, the often occurring beads along the fibers have not yet been investigated in detail. It can be assumed that such beads will support domain wall formation due to a reduction of the relative impact of the shape anisotropy, in this way influencing magnetization reversal along the fiber. Here, we simulate magnetization reversal processes in iron, nickel, cobalt and magnetite fibers with a bead in the middle, produced in three typical dimensions gained by electrospinning. In most cases a vortex state occurs during magnetization reversal, independent from the material and the dimensions. For some angular orientations of the external magnetic field, double-vortex or meander states are visible, usually also followed by vortex states. These simulations underline the strong and highly reliable impact of beads along electrospun fibers, making these structures useful for data storage, transport and other applications. article_number: '167855' article_type: original author: - first_name: Fedi full_name: Amini, Fedi last_name: Amini - first_name: Tomasz full_name: Blachowicz, Tomasz last_name: Blachowicz - first_name: Andrea full_name: Ehrmann, Andrea id: '223776' last_name: Ehrmann orcid: 0000-0003-0695-3905 orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/105571785 citation: alphadin: 'Amini, Fedi ; Blachowicz, Tomasz ; Ehrmann, Andrea: Systematic study of magnetization reversal in beaded fibers from different magnetic materials. In: Journal of Magnetism and Magnetic Materials Bd. 529, Elsevier BV (2021)' ama: Amini F, Blachowicz T, Ehrmann A. Systematic study of magnetization reversal in beaded fibers from different magnetic materials. Journal of Magnetism and Magnetic Materials. 2021;529. doi:10.1016/j.jmmm.2021.167855 apa: Amini, F., Blachowicz, T., & Ehrmann, A. (2021). Systematic study of magnetization reversal in beaded fibers from different magnetic materials. Journal of Magnetism and Magnetic Materials, 529. https://doi.org/10.1016/j.jmmm.2021.167855 bibtex: '@article{Amini_Blachowicz_Ehrmann_2021, title={Systematic study of magnetization reversal in beaded fibers from different magnetic materials}, volume={529}, DOI={10.1016/j.jmmm.2021.167855}, number={167855}, journal={Journal of Magnetism and Magnetic Materials}, publisher={Elsevier BV}, author={Amini, Fedi and Blachowicz, Tomasz and Ehrmann, Andrea}, year={2021} }' chicago: Amini, Fedi, Tomasz Blachowicz, and Andrea Ehrmann. “Systematic Study of Magnetization Reversal in Beaded Fibers from Different Magnetic Materials.” Journal of Magnetism and Magnetic Materials 529 (2021). https://doi.org/10.1016/j.jmmm.2021.167855. ieee: F. Amini, T. Blachowicz, and A. Ehrmann, “Systematic study of magnetization reversal in beaded fibers from different magnetic materials,” Journal of Magnetism and Magnetic Materials, vol. 529, 2021. mla: Amini, Fedi, et al. “Systematic Study of Magnetization Reversal in Beaded Fibers from Different Magnetic Materials.” Journal of Magnetism and Magnetic Materials, vol. 529, 167855, Elsevier BV, 2021, doi:10.1016/j.jmmm.2021.167855. short: F. Amini, T. Blachowicz, A. Ehrmann, Journal of Magnetism and Magnetic Materials 529 (2021). date_created: 2022-01-01T14:27:47Z date_updated: 2022-01-01T15:01:28Z department: - _id: '103' doi: 10.1016/j.jmmm.2021.167855 intvolume: ' 529' keyword: - Magnetic nanostructures Micromagnetic simulation Magnetization reversal Iron Nickel Cobalt Magnetite Vortex state Domain walls Shape anisotropy language: - iso: eng main_file_link: - open_access: '1' url: https://doi.org/10.1016/j.jmmm.2021.167855 oa: '1' publication: Journal of Magnetism and Magnetic Materials publication_identifier: issn: - '03048853' publication_status: published publisher: Elsevier BV quality_controlled: '1' status: public title: Systematic study of magnetization reversal in beaded fibers from different magnetic materials type: journal_article user_id: '223776' volume: 529 year: '2021' ... --- _id: '669' abstract: - lang: eng text: Magnetic vortices belong to the possibilities to store information in magnetic structures. Understanding their nucleation and propagation is also of interest in basic research. While vortices are usually examined in particles of homogeneous material, here we give an overview of the impact of borders between two materials, i.e. iron and permalloy, on magnetization reversal and vortex formation in double-wedges as well as adjacent rectangles of different thickness. While former investigations of pure iron nanoparticles of similar dimensions revealed different magnetization reversal magnetisms without vortex, with one or two vortices, the addition of a permalloy part stabilized the magnetization reversal so that in all situations under investigation, a single vortex was observed. Our simulations underline the technological importance of such double-material structures for the preparation of nanostructures for storage devices with reliable magnetization reversal processes, stable against erroneous modifications of nanoparticle dimensions and magnetic field orientations. article_number: '167294' article_type: original author: - first_name: Devika full_name: Sudsom, Devika last_name: Sudsom - first_name: Tomasz full_name: Blachowicz, Tomasz last_name: Blachowicz - first_name: Lothar full_name: Hahn, Lothar last_name: Hahn - first_name: Andrea full_name: Ehrmann, Andrea id: '223776' last_name: Ehrmann orcid: 0000-0003-0695-3905 citation: alphadin: 'Sudsom, Devika ; Blachowicz, Tomasz ; Hahn, Lothar ; Ehrmann, Andrea: Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems. In: Journal of Magnetism and Magnetic Materials Bd. 514 (2020)' ama: Sudsom D, Blachowicz T, Hahn L, Ehrmann A. Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems. Journal of Magnetism and Magnetic Materials. 2020;514. doi:10.1016/j.jmmm.2020.167294 apa: Sudsom, D., Blachowicz, T., Hahn, L., & Ehrmann, A. (2020). Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems. Journal of Magnetism and Magnetic Materials, 514. https://doi.org/10.1016/j.jmmm.2020.167294 bibtex: '@article{Sudsom_Blachowicz_Hahn_Ehrmann_2020, title={Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems}, volume={514}, DOI={10.1016/j.jmmm.2020.167294}, number={167294}, journal={Journal of Magnetism and Magnetic Materials}, author={Sudsom, Devika and Blachowicz, Tomasz and Hahn, Lothar and Ehrmann, Andrea}, year={2020} }' chicago: Sudsom, Devika, Tomasz Blachowicz, Lothar Hahn, and Andrea Ehrmann. “Vortex Nucleation and Propagation in Magnetic Double-Wedges and Semi-Squares for Reliable Quaternary Storage Systems.” Journal of Magnetism and Magnetic Materials 514 (2020). https://doi.org/10.1016/j.jmmm.2020.167294. ieee: D. Sudsom, T. Blachowicz, L. Hahn, and A. Ehrmann, “Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems,” Journal of Magnetism and Magnetic Materials, vol. 514, 2020. mla: Sudsom, Devika, et al. “Vortex Nucleation and Propagation in Magnetic Double-Wedges and Semi-Squares for Reliable Quaternary Storage Systems.” Journal of Magnetism and Magnetic Materials, vol. 514, 167294, 2020, doi:10.1016/j.jmmm.2020.167294. short: D. Sudsom, T. Blachowicz, L. Hahn, A. Ehrmann, Journal of Magnetism and Magnetic Materials 514 (2020). date_created: 2021-01-03T16:51:38Z date_updated: 2021-05-21T07:09:59Z department: - _id: '103' doi: 10.1016/j.jmmm.2020.167294 intvolume: ' 514' keyword: - Magnetic nanostructures - Wedges - Micromagnetic simulation - Vortex - Magnetization reversal - Iron - Permalloy - Lithography language: - iso: eng publication: Journal of Magnetism and Magnetic Materials publication_identifier: issn: - 0304-8853 publication_status: published quality_controlled: '1' status: public title: Vortex nucleation and propagation in magnetic double-wedges and semi-squares for reliable quaternary storage systems type: journal_article user_id: '237837' volume: 514 year: '2020' ... --- _id: '635' abstract: - lang: eng text: Magnetic vortex structures are of high technological relevance due to their possible application in magnetic memory. Moreover, investigating magnetization reversal via vortex formation is an important topic in basic research. Typically, such vortices are only investigated in homogeneous magnetic materials of diverse shapes. Here, we report for the first time on micromagnetic simulation of vortex formation in magnetic bow-tie nanostructures, comprising alternating parts from iron and permalloy, investigated for two different thicknesses and under different angles of the external magnetic field. While no vortex was found in pure permalloy square, nanoparticles of the dimensions investigated in this study and in case of iron only a relatively thick sample allowed for vortex formation, different numbers of vortices and antivortices were found in the bow-tie structures prepared from both materials, depending on the angular field orientation and the sample thickness. By stabilizing more than one vortex in a confined nanostructure, it is possible to store more than one bit of information in it. Our micromagnetic simulations reveal that such bi-material structures are highly relevant not only for basic research, but also for data storage applications. article_number: '5' article_type: original author: - first_name: Devika full_name: Sudsom, Devika last_name: Sudsom - first_name: Irén full_name: Juhász Junger, Irén last_name: Juhász Junger - first_name: Christoph full_name: Döpke, Christoph last_name: Döpke - first_name: Tomasz full_name: Blachowicz, Tomasz last_name: Blachowicz - first_name: Lothar full_name: Hahn, Lothar last_name: Hahn - first_name: Andrea full_name: Ehrmann, Andrea id: '223776' last_name: Ehrmann orcid: 0000-0003-0695-3905 citation: alphadin: 'Sudsom, Devika ; Juhász Junger, Irén ; Döpke, Christoph ; Blachowicz, Tomasz ; Hahn, Lothar ; Ehrmann, Andrea: Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures. In: Condensed Matter Bd. 5 (2020), Nr. 1' ama: Sudsom D, Juhász Junger I, Döpke C, Blachowicz T, Hahn L, Ehrmann A. Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures. Condensed Matter. 2020;5(1). doi:10.3390/condmat5010005 apa: Sudsom, D., Juhász Junger, I., Döpke, C., Blachowicz, T., Hahn, L., & Ehrmann, A. (2020). Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures. Condensed Matter, 5(1). https://doi.org/10.3390/condmat5010005 bibtex: '@article{Sudsom_Juhász Junger_Döpke_Blachowicz_Hahn_Ehrmann_2020, title={Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures}, volume={5}, DOI={10.3390/condmat5010005}, number={15}, journal={Condensed Matter}, author={Sudsom, Devika and Juhász Junger, Irén and Döpke, Christoph and Blachowicz, Tomasz and Hahn, Lothar and Ehrmann, Andrea}, year={2020} }' chicago: Sudsom, Devika, Irén Juhász Junger, Christoph Döpke, Tomasz Blachowicz, Lothar Hahn, and Andrea Ehrmann. “Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures.” Condensed Matter 5, no. 1 (2020). https://doi.org/10.3390/condmat5010005. ieee: D. Sudsom, I. Juhász Junger, C. Döpke, T. Blachowicz, L. Hahn, and A. Ehrmann, “Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures,” Condensed Matter, vol. 5, no. 1, 2020. mla: Sudsom, Devika, et al. “Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures.” Condensed Matter, vol. 5, no. 1, 5, 2020, doi:10.3390/condmat5010005. short: D. Sudsom, I. Juhász Junger, C. Döpke, T. Blachowicz, L. Hahn, A. Ehrmann, Condensed Matter 5 (2020). date_created: 2021-01-03T14:42:18Z date_updated: 2021-05-19T14:01:34Z ddc: - '530' department: - _id: '103' doi: 10.3390/condmat5010005 file: - access_level: open_access content_type: application/pdf creator: aehrmann date_created: 2021-01-03T14:41:31Z date_updated: 2021-01-03T14:41:31Z file_id: '636' file_name: _2020_Sudsom_CondMatter5_5_corr.pdf file_size: 4886370 relation: main_file success: 1 file_date_updated: 2021-01-03T14:41:31Z funded_apc: '1' has_accepted_license: '1' intvolume: ' 5' issue: '1' keyword: - magnetic nanostructures - micromagnetic simulation - bow-tie structure - vortex - magnetization reversal - iron - permalloy - lithography language: - iso: eng oa: '1' publication: Condensed Matter publication_identifier: issn: - 2410-3896 publication_status: published quality_controlled: '1' status: public title: Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures type: journal_article user_id: '237837' volume: 5 year: '2020' ...