Impact of Strain and Morphology on Magnetic Properties of Fe₃O₄/NiO Bilayers Grown on Nb:SrTiO₃(001) and MgO(001)
Autor(en): | Kuschel, Olga Pathé, Nico Schemme, Tobias Ruwisch, Kevin Rodewald, Jari Buss, Ralph Bertram, Florian Kuschel, Timo Kuepper, Karsten Wollschläger, Joachim |
Affiliationen: | Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. oschuckm@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. npathe@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. toschemm@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. kruwisch@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. jarodewa@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. rbuss@uos.de. Deutsches Elektronen-Synchrotron (DESY), Photon Science, 22607 Hamburg, Germany. florian.bertram@desy.de. Center for Spinelectronic Materials and Devices, Department of Physics, Bielefeld University, 33615 Bielefeld, Germany. tkuschel@physik.uni-bielefeld.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. kkuepper@uos.de. Department of Physics and Center of Physics and Chemistry of New Materials, Osnabrück University, 49076 Osnabrück, Germany. jwollsch@uos.de. | Erscheinungsdatum: | 2018 | Journal: | Materials / MDPI | Volumen: | 11 | Ausgabe: | 7 | Zusammenfassung: | We present a comparative study of the morphology and structural as well as magnetic properties of crystalline Fe₃O₄/NiO bilayers grown on both MgO(001) and SrTiO₃(001) substrates by reactive molecular beam epitaxy. These structures were investigated by means of X-ray photoelectron spectroscopy, low-energy electron diffraction, X-ray reflectivity and diffraction, as well as vibrating sample magnetometry. While the lattice mismatch of NiO grown on MgO(001) was only 0.8%, it was exposed to a lateral lattice mismatch of −6.9% if grown on SrTiO₃. In the case of Fe₃O₄, the misfit strain on MgO(001) and SrTiO₃(001) amounted to 0.3% and −7.5%, respectively. To clarify the relaxation process of the bilayer system, the film thicknesses of the magnetite and nickel oxide films were varied between 5 and 20 nm. While NiO films were well ordered on both substrates, Fe₃O₄ films grown on NiO/SrTiO₃ exhibited a higher surface roughness as well as lower structural ordering compared to films grown on NiO/MgO. Further, NiO films grew pseudomorphic in the investigated thickness range on MgO substrates without any indication of relaxation, whereas on SrTiO₃ the NiO films showed strong strain relaxation. Fe₃O₄ films also exhibited strong relaxation, even for films of 5 nm thickness on both NiO/MgO and NiO/SrTiO₃. The magnetite layers on both substrates showed a fourfold magnetic in-plane anisotropy with magnetic easy axes pointing in 100 directions. The coercive field was strongly enhanced for magnetite grown on NiO/SrTiO₃ due to the higher density of structural defects, compared to magnetite grown on NiO/MgO. |
DOI: | 10.3390/ma11071122 | Externe URL: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073869 |
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geprüft am 13.05.2024