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Subject: search.filters.subject.530Publication Type: search.filters.UBSTyp.Abschlussarbeit (Master)Start date: 2013End date: 2019Institute: search.filters.UBSInstitut.1. Physikalisches InstitutAuthor: search.filters.author.Höfel, Udo

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    Size and temporal distributions in nanoscale magnetic materials via advanced extraction methods
    (2015) Höfel, Udo
    Magnetic nanoparticles possess a multitude of fields of application, for example in biotechnology and utilization as (magnetically) easily separable catalysts. Among the diverse fabrication methods that allow the production of nanoparticles with magnetic properties respectively a chemical composition tailored for a specific task one can find the bottom-up sol-gel dip-coating technique, with which the CoNi nanoparticles embedded in silica were created. Those nanoparticles exhibit a wavelength dependent coercivity if irradiated with laser light. The mentioned behaviour was modeled via an extended, single domain ferromagnetic Stoner-Wohlfarth model implemented in Mathematica. Therein the amount of permitted angles between the nanoparticles easy axis and the external applied field can be limited to arbitrary starting and ending angles. Furthermore, a particle size distribution dependent model for superparamagnetic magnetisation measurements is discussed and its implementation in Mathematica documented. To complement the models programed in Mathematica the extended Jiles-Atherton model that rules out unphysical behaviour and allows the simulation of hystereses was implemented, such that the models available comprise superparamagnetic, single and multi domain ferromagnetic behaviour. Another simple to set up, top-down and „green“ production method is laser ablation sythesis in solution (LASiS). Nitinol (NiTi) nanoparticles created with this technique are of great interest as nitinol shows some exceptional properties, exempli gratia a shape memory, a high resistance to material fatigue and biocompatibility. Thus an extensive (magnetic) characterisation of these nanoparticles is carried out that should ease further production of task specific nanoparticles. Hence the influence of the LASiS liquid on the magnetic properties of the nanoparticles was also analysed. The impact of the laser power on the magnetic behaviour was scrutinized on iron nanoparticles, such that in conclusion some of the „knobs“ that allow tailoring of the properties of the nanoparticles are better understood and therefore grant a more precise parameter choice at the time of fabrication.