|
|
Magneto-optical investigation of spintronic materials
Vojáček, Libor ; Flajšman, Lukáš (referee) ; Arregi Uribeetxebarria, Jon Ander (advisor)
Magnetooptický Kerrův jev představuje užitečný nástroj pro zkoumání magnetických vlastností kovových povrchů. Jeho využití při měření procesu přepínání magnetizace vnějším magnetickým polem nám může poskytnout cennou informaci o magnetické anizotropii zkoumané látky. V předložené práci se zabýváme teoretickými aspekty procesu přepínání magnetizace a změny polarizace světla při odrazu od magnetických povrchů. Dále je popsána optická sestava založená na modulaci polarizace světla schopná měřit magnetooptické veličiny s vysokou citlivostí. Tento přístroj byl sestaven modifikací již existující, podobné optické sestavy. Funkčnost zařízení byla ověřena měřeními na tenkých magnetických vrstvách. Získaná data pomáhají odhalit vlastnosti tenkých metamagnetických vrstev z FeRh, materiálu s potenciálními aplikacemi pro spintroniku.
|
|
|
Study of martensitic tranformation in Co doped NiMnGa films by optical and magnetooptical methods
Nowak, Lukáš ; Veis, Martin (advisor) ; Hamrle, Jaroslav (referee)
Martenzitic transformation is responsible for multiferroic behaviour of mag- netic shape memory effect. However, the origin of the transformation is not yet fully understood. Magnetic shape memory materials in general offer broad spectrum of possible applications. NiMnGa is the prototype compound of these materials. Particular changes in the electronic structure are the origin of marten- zitic transformation which is the key to magnetic shape memory effect. There- fore, the optical and magneto-optical methods are the ideal tools for its analysis. Studied samples were prepared using magnetron sputtering on MgO substrate. Measurements of the Kerr effect at polar configuration and normal light in- cidence were done using rotating analyzer method. Experimental results, in- cluding spectral ellipsometry and temperature dependent measurements, were compared with theoretical models and then discussed. 1
|
|
|
Optical response of magnetic materials
Wagenknecht, David ; Ostatnický, Tomáš (advisor)
David Wagenknecht: Abstract of a diploma thesis Optical response of magnetic materials, 2014 Magnetooptical properties of anisotropic semiconductors are studied to describe asymmetry of Ga1−xMnxAs, because theoretical calculations predict extraordinary behaviour of reflectivity. Analytical formulae to describe materials with non-diagonal permittivity are derived and they are used for the numerical calculations to describe the optical response of the samples available for the measurement. The transversal Kerr effect is calculated and it exhibits asymmetry in both rotation of the plane of polarization and ellipticity of circularly polarized light due to asymmetry in reflectivity. Moreover, longitudinal and polar magnetization are studied because of the influence on the observability of the phenomena. Results are not only used to discuss conditions, which must be satisfied to prove the asymmetry, but also the actual experimental setup is designed to prepare the measurement. 1
|
|
|
Magneto-optic response of layered media
Kunt, Ota ; Ostatnický, Tomáš (advisor) ; Antoš, Roman (referee)
Optical response of materials strongly depends on their magnetic properties. This phenomenon is also used in materials in the form of thin layers and multi- layers. Using cited literature we summarize theory needed to calculate magneto- optical response of multilayers. The calculation is based on Maxwell equations and magnetic materials are described with effective permittivity tensor. Jones formalism is used to describe polarised light and Yeh formalism is used to de- scribe multilayer response. A program using presented theory was developed and calculations for concrete structure were made. Multilayer parameters were cho- sen to correspond with those of a sample whose magneto-optical response was measured at the Department of Chemical Physics and Optics, MFF UK. 1
|
|
|
Optical response of magnetic materials
Wagenknecht, David ; Ostatnický, Tomáš (advisor) ; Antoš, Roman (referee)
David Wagenknecht: Abstract of a diploma thesis Optical response of magnetic materials, 2014 Magnetooptical properties of anisotropic semiconductors are studied to describe asymmetry of Ga1−xMnxAs, because theoretical calculations predict extraordinary behaviour of reflectivity. Analytical formulae to describe materials with non-diagonal permittivity are derived and they are used for the numerical calculations to describe the optical response of the samples available for the measurement. The transversal Kerr effect is calculated and it exhibits asymmetry in both rotation of the plane of polarization and ellipticity of circularly polarized light due to asymmetry in reflectivity. Moreover, longitudinal and polar magnetization are studied because of the influence on the observability of the phenomena. Results are not only used to discuss conditions, which must be satisfied to prove the asymmetry, but also the actual experimental setup is designed to prepare the measurement. 1
|
|
|
Dynamics of spin polarization in ferromagnetic semiconductors
Šubrt, Jiří
This work was devoted to the measurement of magnetooptical effects in ferromagnetic semiconductors. We analyzed in detail the measurement technique based on a photoelastic modulator and we constructed an experimental setup that enables to measure the spectra of magnetic circular dichroism (MCD), magnetic circular birefringence (MCB), magnetic linear dichroism (MLD), and magnetic linear birefringence (MLB). This setup was used for the measurement of magnetooptical spectra of several samples of ferromagnetic semiconductors (Ga,Mn)As and (Ga,Mn)(As,P).
|
guest ::
