Browsing by Author "Khaydukov, Y"

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    Element-specific depth profile of magnetism and stoichiometry at the La0.67Sr0.33MnO3/BiFeO3 interface
    (American Physical Society, 2014-07-11) Bertinshaw, J; Brück, S; Lott, D; Fritzsche, H; Khaydukov, Y; Soltwedel, O; Keller, T; Goering, E; Audehm, P; Cortie, DL; Hutchison, WD; Ramasse, QM; Arredondo, M; Maran, R; Nagarajan, V; Klose, F; Ulrich, C
    Depth-sensitive magnetic, structural, and chemical characterization is important in the understanding and optimization of physical phenomena emerging at the interfaces of transition metal oxide heterostructures. In a simultaneous approach we have used polarized neutron and resonant x-ray reflectometry to determine the magnetic profile across atomically sharp interfaces of ferromagnetic La0.67Sr0.33MnO3/multiferroic BiFeO3 bilayers with subnanometer resolution. In particular, the x-ray resonant magnetic reflectivity measurements at the Fe and Mn resonance edges allowed us to determine the element-specific depth profile of the ferromagnetic moments in both the La0.67Sr0.33MnO3 and BiFeO3 layers. Our measurements indicate a magnetically diluted interface layer within the La0.67Sr0.33MnO3 layer, in contrast to previous observations on inversely deposited layers [P. Yu et al., Phys. Rev. Lett. 105, 027201 (2010)]. Additional resonant x-ray reflection measurements indicate a region of altered Mn and O content at the interface, with a thickness matching that of the magnetic diluted layer, as the origin of the reduction of the magnetic moment.© 2014, American Physical Society.
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    Enhanced magnetism in field-cooled [Ni80Fe20/Mn]3 multilayers studied using polarized neutron reflectometry
    (IOP Publishing, 2016-05-11) Uilhoorn, W; Callori, SJ; Cortie, DL; Su, HC; Khaydukov, Y; Lin, KW; Klose, F
    Here, the interfacial magnetic coupling in an exchange biased [Ni80Fe20/Mn]3 multilayer system has been studied using polarized neutron reflectometry. Previous results on this system indicate the importance of the coupling between the Fe-Mn and Ni-Mn orbitals at the layer interfaces. Magnetic depth profiles of the multilayer were measured at low temperatures under field-cooled and zero-field-cooled conditions. While no definitive interfacial state was found, a magnetic moment enhancement of roughly 20-30% in the applied field direction was observed throughout the bulk of the NiFe layers in the field-cooled state as compared to the zero-field-cooled measurements. The origin of this enhancement also likely stems from Fe-Mn and Ni-Mn orbital coupling, but due to the interfacial roughnesses of the sample, the areas where this coupling plays an important role is no longer confined to the interface. © The Authors - Open Access CC-BY 3.0
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    Structure and magnetism of ultra-small cobalt particles assembled at titania surfaces by ion beam synthesis
    (Elsevier, 2021-12) Bake, A; Rezoanur Rahman, M; Evans, PJ; Cortie, MB; Nancarrow, M; Abrudan, R; Radu, F; Khaydukov, Y; Causer, GL; Callori, SJ; Livesey, KL; Mitchell, DRG; Pastuovic, Z; Wang, XL; Cortie, DL
    Metallic cobalt nanoparticles offer attractive magnetic properties but are vulnerable to oxidation, which suppresses their magnetization. In this article, we report the use of ion beam synthesis to produce ultra-small, oxidation-resistant, cobalt nanoparticles embedded within substoichiometric TiO2-δ thin films. Using high fluence implantation of cobalt at 20–60 keV, the particles were assembled with an average size of 1.5 ± 1 nm. The geometry and structure of the nanoparticles were studied using scanning transmission electron microscopy. Near-edge X-ray fluorescence spectroscopy on the L2,3 Co edges confirms that the majority of the particles beneath the surface are metallic, unoxidised cobalt. Further evidence of the metallic nature of the small particles is provided via their high magnetization and superparamagnetic response between 3 and 300 K with a low blocking temperature of 4.5 K. The magnetic properties were studied using a combination of vibrating sample magnetometry, element-resolved X-ray magnetic circular dichroism, and depth-resolved polarised neutron reflectometry. These techniques provide a unified picture of the magnetic metallic Co particles. We argue, based on these experimental observations and thermodynamic calculations, that the cobalt is protected against oxidation beneath the surface of titania owing to the enthalpic stability of TiO2 over CoO which inhibits solid state reactions. Crown Copyright © 2021 Published by Elsevier B.V.
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    Ultra-small cobalt particles embedded in titania by ion beam synthesis: additional datasets including electron microscopy, neutron reflectometry, modelling outputs and particle size analysis
    (Elsevier, 2022-02) Bake, A; Rahman, R; Evans, PJ; Cortie, MB; Nancarrow, M; Abrudan, R; Radu, F; Khaydukov, Y; Causer, GL; Livesey, KL; Callori, SJ; Mitchell, DRG; Pastuovic, Z; Wang, XL; Cortie, DL
    This Data-in-brief article includes datasets of electron microscopy, polarised neutron reflectometry and magnetometry for ultra-small cobalt particles formed in titania thin films via ion beam synthesis. Raw data for polarised neutron reflectometry, magnetometry and the particle size distribution are included and made available on a public repository. Additional elemental maps from scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) are also presented. Data were obtained using the following types of equipment: the NREX and PLATYPUS polarised neutron reflectometers; a Quantum Design Physical Property Measurement System (14 T); a JEOL JSM-6490LV SEM, and a JEOL ARM-200F scanning transmission electron microscope (STEM). The data is provided as supporting evidence for the article in Applied Surface Science (A. Bake et al., Appl. Surf. Sci., vol. 570, p. 151068, 2021, DOI 10.1016/j.apsusc.2021.151068), where a full discussion is given. The additional supplementary reflectometry and modelling datasets are intended to assist future scientific software development of advanced fitting algorithms for magnetization gradients in thin films. Crown Copyright © 2021 - Open Access CC BY-NC-ND