Kurzbeschreibung
(Englisch)
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Seeking the understanding to control the position, the orientation, the spacing, and the mobility of domain walls in multiferroic thin films.
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, CH, CZ, DE, EL, ES, FI, FR, IE, IT, LT, NL, PL, PT, RO, RS, SI, SK, UK
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Abstract
(Englisch)
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The ultimate goal of the project is to understand how to control the position, orientation, spacing and mobility of domain walls in bismuth ferrite, lead zirconate titanate and other ferroelectrics in order to enhance functionality of these materials and ideally introduce new applications based on the developed understanding. The main effort and results during the 3rd year of the project are the conceptualizing and generalizing of the route to obtain controlled domain wall patterns 'on-demand'. The model material was PZT, which is the most widely used ferroelectric material. One-dimensional arrays of very narrow domain patterns of the so-called 'a'-domains having width down to 10 nm and below were obtained. Previous efforts to manipulate a-domain patterns faced largely immobile structures. Thanks to the low defect density in our films, we were able to overcome these difficulties and show creation and modification of the highly flexible domain patterns in a very selective way. By the application of an electric field not only the electrostatic conditions but also the strain state of the films could be adjusted. This possibility, we hope, will be useful in future agile devices where the domain and domain-wall structure/pattern can be changed during operation. Additional results that involved short term visits through the COST 904 program include: (1) Experimental detailed study of 109o domain walls in BFO which lead to development of understanding of the conduction mechanism: A complex model involving defect-mediated hopping and polarization-controlled injection through the top interface was shown to be consistent with the observed conduction behavior. (2) Following the successful deposition of the ferroelectric polymer PVDF, control of magnetic domains has been demonstrated at room temperature on ultrathin layers of magnetic metal (Co). The ferroelectric-gate-driven change of electron density in the interface-adjacent layer of the Co channel was sufficient to change significantly the magnetic anisotropy.
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