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Study of magnonic crystals in a frequency domain
Turčan, Igor ; Hrabec, Aleš (oponent) ; Urbánek, Michal (vedoucí práce)
Characterization of magnetodynamic properties of nanomagnets and nanostructured magnetic materials requires methods appropriate for probing the typical timescales of these systems, i.e. in the sub-nanosecond range. The lack of appropriate time-domain characterization techniques is linked to the limits of current electronics. Other possible approach is to use the frequency domain characterization in GHz range. The most common frequency domain characterization technique is the ferromagnetic resonance (FMR) measurement. From FMR spectra it is possible to extract valuable information about the magnetic system: the damping parameter, saturation magnetization etc. The method we utilize for detection of spin-wave excitations aims for the simplification of the characterization experiment. We employ the thermoelectric detection of spin waves in magnetic strips via anomalous Nernst effect. The method is based on the heat generation inside a magnetic film due to the relaxation of spin waves to the lattice. The dissipation of spin-wave energy heats the magnetic strip and creates a temperature gradient towards the substrate (perpendicular to the surface). This leads to generation of an electric field perpendicular to both the temperature gradient and the magnetization direction. The voltage is usually in the V range, hence it can be measured with common laboratory equipment. Despite its simplicity, this method yields very interesting results and can be used for characterization of magnonic waveguides, magnonic metamaterials, spin-wave emitters and other spin-wave devices.
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Magnetic insulators with hexagonal and cubic structure
Soroka, Miroslav ; Tyrpekl, Václav (vedoucí práce) ; Pinkas, Jiří (oponent) ; Sedmidubský, David (oponent)
Název práce: Magnetické izolátory s hexagonální a kubickou strukturou Autor: Mgr. Miroslav Soroka Katedra: Katedra anorganické chemie, PřF UK, Praha Vedoucí doktorské práce: RNDr. Václav Tyrpekl, Ph.D. Konzultanti: Ing. Josef Buršík, CSc., RNDr. Karel Knížek, Dr. Abstrakt Předložená práce se zabývá přípravou tenkých vrstev magnetických izolátorů s hexagonální a kubickou strukturou na bázi oxidů přechodných kovů pomocí metody depozice z kapalné fáze (CSD) a studiem jejich fyzikálních vlastností. Tenké vrstvy hexagonálních feritů typu Z (Sr3-xBaxCo2Fe24O41) a W (SrCo2-xZnxFe16O27) byly připravené se záměrem studovat magnetické vlastnosti, magneto-elektrický jev (ME) a spinový Seebeckův jev (SSE). Studium SSE, jakožto spin-caloritronického fenoménu, na feritech bylo doplněno studiem SSE ve vrstvách ε-Fe2-xAlxO3 a anomálního Nernstova jevu (ANE) v La0.7Sr0.3CoO3. V rámci optimalizace přípravy tenkých vrstev bylo využito více variant CSD procesů založených na různých typech prekurzorů lišících se svými chemickými vlastnostmi: alkoxidy kovů, soli 2-ethylhexanové kyseliny a citrátové komplexy kovů. Připravené materiály byly strukturně charakterizovány pomoci práškové rentgenové difrakce (pXRD). Orientace připravených vrstev byla charakterizována pomocí ω-křivek a měření φ-skenů. Ke studiu mikrostruktury a...
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Study of magnonic crystals in a frequency domain
Turčan, Igor ; Hrabec, Aleš (oponent) ; Urbánek, Michal (vedoucí práce)
Characterization of magnetodynamic properties of nanomagnets and nanostructured magnetic materials requires methods appropriate for probing the typical timescales of these systems, i.e. in the sub-nanosecond range. The lack of appropriate time-domain characterization techniques is linked to the limits of current electronics. Other possible approach is to use the frequency domain characterization in GHz range. The most common frequency domain characterization technique is the ferromagnetic resonance (FMR) measurement. From FMR spectra it is possible to extract valuable information about the magnetic system: the damping parameter, saturation magnetization etc. The method we utilize for detection of spin-wave excitations aims for the simplification of the characterization experiment. We employ the thermoelectric detection of spin waves in magnetic strips via anomalous Nernst effect. The method is based on the heat generation inside a magnetic film due to the relaxation of spin waves to the lattice. The dissipation of spin-wave energy heats the magnetic strip and creates a temperature gradient towards the substrate (perpendicular to the surface). This leads to generation of an electric field perpendicular to both the temperature gradient and the magnetization direction. The voltage is usually in the V range, hence it can be measured with common laboratory equipment. Despite its simplicity, this method yields very interesting results and can be used for characterization of magnonic waveguides, magnonic metamaterials, spin-wave emitters and other spin-wave devices.
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