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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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Construction of pseudoscalar meson amplitudes in chiral perturbation theory using a dispersive approach
Zdráhal, Martin ; Novotný, Jiří (advisor) ; Bijnens, Johan (referee) ; Ecker, Gerhard (referee)
Title: Construction of pseudoscalar meson amplitudes in chiral perturbation theory using a dispersive approach Author: Martin Zdráhal Department: Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: RNDr. Jiří Novotný, CSc. Abstract: We have developed a method enabling a construction of two-loop 2 → 2 scatter- ing amplitudes of pseudoscalar mesons based on the dispersion and the unitarity relations. This method is illustrated on the construction of the amplitudes of all such processes in chiral perturbation theory in isospin limit taking into account strong interactions only. Then it was used for the construction of ππ scattering amplitudes and of K → 3π and η → 3π decay amplitudes including isospin breaking effects induced by different masses of the particles belonging to the same isomultiplet. These parametrizations are prepared for various phenomenological analyses of the ππ scattering lengths and of the isospin breaking effects, both of which could pro- vide us important information for the understanding of quantum chromody- namics at low energies. Finally, we have performed the phenomenological study of η → 3π decay and obtained a value of the quark mass ratio 1/R = (md − mu)/(ms − ˆm). Our conservative estimate is R = 39.6+2.5 −5.1....
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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.
|
|
|
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.
|
|
|
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.
|
|
|
Construction of pseudoscalar meson amplitudes in chiral perturbation theory using a dispersive approach
Zdráhal, Martin ; Novotný, Jiří (advisor) ; Bijnens, Johan (referee) ; Ecker, Gerhard (referee)
Title: Construction of pseudoscalar meson amplitudes in chiral perturbation theory using a dispersive approach Author: Martin Zdráhal Department: Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: RNDr. Jiří Novotný, CSc. Abstract: We have developed a method enabling a construction of two-loop 2 → 2 scatter- ing amplitudes of pseudoscalar mesons based on the dispersion and the unitarity relations. This method is illustrated on the construction of the amplitudes of all such processes in chiral perturbation theory in isospin limit taking into account strong interactions only. Then it was used for the construction of ππ scattering amplitudes and of K → 3π and η → 3π decay amplitudes including isospin breaking effects induced by different masses of the particles belonging to the same isomultiplet. These parametrizations are prepared for various phenomenological analyses of the ππ scattering lengths and of the isospin breaking effects, both of which could pro- vide us important information for the understanding of quantum chromody- namics at low energies. Finally, we have performed the phenomenological study of η → 3π decay and obtained a value of the quark mass ratio 1/R = (md − mu)/(ms − ˆm). Our conservative estimate is R = 39.6+2.5 −5.1....
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