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Spin wave spectroscopy in ferromagnet-superconductor hybrid structures
Pribytova, Ekaterina ; Davídková, Kristýna (referee) ; Urbánek, Michal (advisor)
Spin wave spectroscopy has emerged as a promising path in the study of ferromagnet-superconductor hybrid structures. These structures exhibit a wide range of spin wave frequencies, spanning from the GHz to the THz regime, making them potential candidates for efficient information transfer without the translational motion of electrons and associated Joule heating. This characteristic positions them as promising candidates for the realization of novel and highly efficient computational concepts. While previous magnonic experiments have predominantly been conducted at room temperature, the growing interest in hybrid systems for quantum computing necessitates the operation of magnonic devices at low temperatures and within the framework of superconducting circuits. The aim of this bachelor's thesis is to explore the possibilities of information transfer using spin waves in ferromagnet-superconductor systems.
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Excitation of exchange spin waves using microwave nano antennas
Davídková, Kristýna ; Holobrádek, Jakub (referee) ; Urbánek, Michal (advisor)
The transmission and processing of information could be carried out by utilizing spin waves in the future. Using the possibility of encoding information into the amplitude and wave phase would lead to the acceleration of complex mathematical operations, while for their efficiency it is necessary to work with spin waves in the exchange mode, which are characterized by a short wavelength. However, exchange mode spin waves are not so easy to generate. This bachelor thesis deals with the generation and detection of exchange spin waves, which is performed using lithographically fabricated nanoantennas on the surface of an iron-yttrium garnet magnetic layer. The bachelor thesis also contains analytical calculations of excitation spectra of the generated nanoantennas of different shapes and sizes, whose model is verified by simulations and experiment.
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Dispersion relation of magnonic crystals with nontrivial spatial distribution of magnetic anisotropy
Wojewoda, Ondřej ; Hamrle,, Jaroslav (referee) ; Flajšman, Lukáš (advisor)
Magnonics is a novel field of research dealing with the physics of spin waves, which are collective excitations of a magnetization. Magnonic crystals, the basic building blocks of magnonic circuits, allow extended control over the spin-wave dispersion. The periodic structure of magnonic crystals results in the formation of a complex band structure with a gap of forbidden frequencies. Periodic structures are conventionally prepared by a local modulation of material thickness or by a step change of saturation magnetization. The presented work deals with the theoretical verification of dispersion relations of magnonic crystals, where the periodicity of the system is achieved by the modulation of the direction of uniaxial magnetic anisotropy and by continuous change of saturation magnetization. For a better insight into the propagation of spin waves in a material with non-homogeneous magnetic properties, a theory describing the refraction and reflection of spin waves at the interface is presented and further verified by numerical simulations.
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Analysis of wave-particle interactions in space plasmas
Černý, Miroslav ; Santolík, Ondřej (advisor) ; Souček, Jan (referee)
This work deals with the linear analysis of plasma waves, especially with the methods of solution of a hot plasma dispersion relation. There are cited some results achieved in the space plasma research and mapped current numerical methods of their analysis. Besides, this work introduces a new numeric procedure, computer code PDRS (Plasma Dispersion Relation Solver), which allows finding solution of a dispersion function of a cold or hot plasma with general distribution function. It also demonstrates the usage of the PDRS methods on real examples of waves in space plasma based on the spacecraft Cluster measurement.
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Excitation of exchange spin waves using microwave nano antennas
Davídková, Kristýna ; Holobrádek, Jakub (referee) ; Urbánek, Michal (advisor)
The transmission and processing of information could be carried out by utilizing spin waves in the future. Using the possibility of encoding information into the amplitude and wave phase would lead to the acceleration of complex mathematical operations, while for their efficiency it is necessary to work with spin waves in the exchange mode, which are characterized by a short wavelength. However, exchange mode spin waves are not so easy to generate. This bachelor thesis deals with the generation and detection of exchange spin waves, which is performed using lithographically fabricated nanoantennas on the surface of an iron-yttrium garnet magnetic layer. The bachelor thesis also contains analytical calculations of excitation spectra of the generated nanoantennas of different shapes and sizes, whose model is verified by simulations and experiment.
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Dispersion relation of magnonic crystals with nontrivial spatial distribution of magnetic anisotropy
Wojewoda, Ondřej ; Hamrle,, Jaroslav (referee) ; Flajšman, Lukáš (advisor)
Magnonics is a novel field of research dealing with the physics of spin waves, which are collective excitations of a magnetization. Magnonic crystals, the basic building blocks of magnonic circuits, allow extended control over the spin-wave dispersion. The periodic structure of magnonic crystals results in the formation of a complex band structure with a gap of forbidden frequencies. Periodic structures are conventionally prepared by a local modulation of material thickness or by a step change of saturation magnetization. The presented work deals with the theoretical verification of dispersion relations of magnonic crystals, where the periodicity of the system is achieved by the modulation of the direction of uniaxial magnetic anisotropy and by continuous change of saturation magnetization. For a better insight into the propagation of spin waves in a material with non-homogeneous magnetic properties, a theory describing the refraction and reflection of spin waves at the interface is presented and further verified by numerical simulations.
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Analysis of wave-particle interactions in space plasmas
Černý, Miroslav ; Santolík, Ondřej (advisor) ; Souček, Jan (referee)
This work deals with the linear analysis of plasma waves, especially with the methods of solution of a hot plasma dispersion relation. There are cited some results achieved in the space plasma research and mapped current numerical methods of their analysis. Besides, this work introduces a new numeric procedure, computer code PDRS (Plasma Dispersion Relation Solver), which allows finding solution of a dispersion function of a cold or hot plasma with general distribution function. It also demonstrates the usage of the PDRS methods on real examples of waves in space plasma based on the spacecraft Cluster measurement.
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Measurement of the Basic Material Characteristics forTransmission of Chain Filter
Melich, Radek
Observing the Sun with birefringent filters is done mainly with filters tuned constantly on some interesting spectral wavelength. However, a new problem that solves tuning of these filters by a temperature change, meets a problem of a insufficient accuracy of dispersion dependences which are used for calculation of transmission at the exact wavelength and the exact temperature. Designing a filter that reaches an extreme small value in its FWHM (e.g. 0.05 nm) it is then very important to determine birefringent dependency with a sufficient accuracy. The paper shows the technique of getting such dependencies, then it mentions a mathematical process suitable for getting the transmission of Solc filter and finally it compares data got from an experiment with computed data.
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