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Temperature-induced phase transition from cycloidal to collinear antiferromagnetism in multiferroic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mm
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In this dissertation core level electron spectroscopy has been employed to study various aspects of metal oxide films grown under ultra-high vacuum conditions. Studies on in situ ion insertion of lithium into thin TiO2 systems were... more
In this dissertation core level electron spectroscopy has been employed to study various aspects of metal oxide films grown under ultra-high vacuum conditions. Studies on in situ ion insertion of lithium into thin TiO2 systems were performed. The electronic and geometric properties are investigated in detail, along with an estimation of charge transfer from Li to Ti. A detailed study of chemical vapour deposition of ZrO2 on Si(100)-(2x1) was performed. ZrO2 is found to be an insulator, i.e. its electronic levels are decoupled from the substrate and the Zr levels are best referenced to the local vacuum level. The alignment of the valence and conduction band has been determined. Combinatorial chemical vapour deposition of TiO2 and ZrO2 on Si(100)-(2x1) was realized. A film with graded stoichiometry consisting of pure TiO2 and ZrO2 on the opposing ends and mixed composition of both oxides in the middle was obtained. A detailed study of the electronic levels revealed that ZrO2 remains an insulator in the monolayer regime and that modification of ZrO2 with a small amount of TiO2 leads to a more symmetric alignment of the bands relative to Si. The influence of a core hole on the O 1s x-ray absorption spectrum in TiO2 and ZrO2 is elucidated. Supported by O 1s photoemission measurements and ab initio calculations it is concluded that the static final state picture as well as dynamical threshold effects must be considered in order to determine the location of the conduction band minimum within the XAS framework. Finally a Co modified Co:ZnO film was shown to display ferromagnetic properties. It could be evidenced that Co with oxygen as nearest neighbours was responsible for the magnetism and not metallic Co.
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Magnetocrystalline anisotropy of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mm
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The potentially most important challenges today are related to energy and the environment. New materials and methods are needed in order to, in a sustainable way, convert and store energy, reduce pollution, and clean the air and water... more
The potentially most important challenges today are related to energy and the environment. New materials and methods are needed in order to, in a sustainable way, convert and store energy, reduce pollution, and clean the air and water from contaminations. In this, nanomaterials and nanocomposites play a key role, and hence knowledge about the relation between synthesis, structure, and properties of nanosystems is paramount.This thesis demonstrates that solution-chemical synthesis, using amine-modified acetates and nitrates, can be used to prepare widely different nanostructured films. By adjusting the synthesis parameters, metals, oxides, and metal–oxide or oxide–oxide nanocomposites were prepared for two systems based on Co and Zn:Fe, respectively, and the films were characterised using diffraction, spectroscopy, and microscopy techniques, and SQUID magnetometry.A variety of crystalline cobalt films—Co metal, CoO, Co3O4, and composites with different metal:oxide ratios—were synthesised. Heat-treatment parameters and control of the film thickness enabled tuning of the phase ratios. Random and layered Co–CoO composites were prepared by utilising different heating rates and gas flow rates together with a morphology effect associated with the furnace tube. The Co–CoO films exhibited exchange bias due to the ferromagnetic–antiferromagnetic interaction between the Co and CoO, whereas variations in e.g. coercivity and exchange bias field were attributed to differences in the structure and phase distribution.Ordered structures of wurtzite ZnO surrounded by amorphous ZnxFeyO were prepared through controlled phase segregation during the heating, which after multiple coating and heating cycles yielded ZnO–ZnxFeyO superlattices. The amorphous ZnxFeyO was a prerequisite for superlattice formation, and it profoundly affected the ZnO phase, inhibiting grain growth and texture, already from 1% Fe. In addition, ZnO–ZnxFeyO exhibited a photocatalytic activity for the oxidation of water that was higher than results reported for pure ZnO, and comparable to recent results reported for graphene-modified ZnO.
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Soft magnetic FeCo alloys are of great interest due to their potential spintronics applications. The magnetic damping parameter plays a vital role in the performance of these spintronics devices. T ...
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In this paper, hard magnetic materials for future use in electrical machines are discussed. Commercialized permanent magnets used today are presented and new magnets are reviewed shortly. Specifically, the magnetic MnAl compound is... more
In this paper, hard magnetic materials for future use in electrical machines are discussed. Commercialized permanent magnets used today are presented and new magnets are reviewed shortly. Specifically, the magnetic MnAl compound is investigated as a potential material for future generator designs. Experimental results of synthesized MnAl, carbon-doped MnAl and calculated values for MnAl are compared regarding their energy products. The results show that the experimental energy products are far from the theoretically calculated values with ideal conditions due to microstructure-related reasons. The performance of MnAl in a future permanent magnet (PM) generator is investigated with COMSOL, assuming ideal conditions. Simplifications, such as using an ideal hysteresis loop based on measured and calculated saturation magnetization values were done for the COMSOL simulation. The results are compared to those for a ferrite magnet and an NdFeB magnet. For an ideal MnAl hysteresis loop, it ...
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The magnetic ground states in highly ordered double perovskites LaSr1−xCaxNiReO6 (x = 0.0, 0.5, 1.0) are studied in view of the Goodenough-Kanamori rules of superexchange interactions in this paper. In LaSrNiReO6, Ni and Re sublattices... more
The magnetic ground states in highly ordered double perovskites LaSr1−xCaxNiReO6 (x = 0.0, 0.5, 1.0) are studied in view of the Goodenough-Kanamori rules of superexchange interactions in this paper. In LaSrNiReO6, Ni and Re sublattices are found to exhibit curious magnetic states separately, but no long range magnetic ordering is achieved. The magnetic transition at ~255 K is identified with the independent Re sublattice magnetic ordering. Interestingly, the sublattice interactions are tuned by modifying the Ni-O-Re bond angles through Ca doping. Upon Ca doping, the Ni and Re sublattices start to display a ferrimagnetically ordered state at low temperature. The neutron powder diffraction data reveals long range ferrimagnetic ordering of the Ni and Re magnetic sublattices along the crystallographic b-axis. The transition temperature of the ferrimagnetic phase increases monotonically with increasing Ca concentration.
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Research Interests: Materials Engineering, Mechanical Engineering, Physics, Condensed Matter Physics, Materials Science, and 12 moreMagnetism, Thin Film, Physical sciences, Magnetic Properties, Temperature Dependence, Squid, Magnetism and Magnetic Materials, Magnetization, Magnetic Circular Dichroism, Magnetic Anisotropy, Magnetometer, and x-ray magnetic circular dichroism (XMCD)
Molecular diagnostics based on magnetic nanobead clustering dynamics monitored using a Blu-ray optomagnetic readout system
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Effect of <i>in situ</i> electric-field-assisted growth on antiphase boundaries in epitaxial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mm
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Evaluating the impact of the potential window on the electrochemical performance of the MnFe2O4 based anode material in Li-ion batteries.
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Research Interests: Pharmacology, Genetics, Materials Science, Molecular Biology, Infectious Diseases, and 15 moreMedicine, DNA, PCR, Magnetic nanoparticles, Detection, Am, Min, MNP, Newcastle disease, Magnetic Nanoparticles, LOOP MEDIATED ISOTHERMAL AMPLIFICATION, Newcastle Disease Virus, Amplicon, Biotinylation, and Fysik
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Radio frequency sputtering by argon ions on a target consisting of tungsten disulphide can create a single layer of the compound on a 4′′ Si-wafer with one W atom per two S atoms when including hydrogen sulphide in the sputtering... more
Radio frequency sputtering by argon ions on a target consisting of tungsten disulphide can create a single layer of the compound on a 4′′ Si-wafer with one W atom per two S atoms when including hydrogen sulphide in the sputtering atmosphere.
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Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron... more
Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds.