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Investigation of spin polarization in semiconductors by laser spectroscopy
Butkovičová, Dagmar ; Němec, Petr (advisor) ; Kadlec, Filip (referee)
This work is devoted to the investigation of a spin polarization in ferromagnetic semiconductor Ga1-xMnxAs with a broad nominal concentration of manganese ions using one method of the ultrafast laser spectroscopy - the time-resolved Kerr rotation. At first, the experimental setup was optimized for the investigation of the dynamics of spin polarized charge carriers in semiconductors which were photo-generated by circularly polarized laser pulses. It was observed that the measured signal is induced by spin-polarized electrons. Due to a small thickness of the investigated ferromagnetic films the measured signal probably monitored the dynamics of fotogenerated electrons in GaAs substrate. Nevertheless, the measured data show that the electron spin dynamics in the substrate is significantly influenced by proximity effect due to the deposited ferromagnetic layer.
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Spatially resolved measurements of magneto-optical Kerr effect in nanostructures
Kletečka, Vojtěch ; Veis, Martin (advisor) ; Butkovičová, Dagmar (referee)
With increasing complexity of devices utilizing magnetic properties of mate- rials grows the need to characterize and further examine these properties. One of the possible ways to do this is utilizing of magnetooptical Kerr effect with Kerr microscope. In the theoretical part of this thesis is at first described response of the electromagnetic wave to the magnetic field in reflection on the ferromagnetic material and then explained the possibility of using the effect in measurements of the response. After that in experimental part is designed and constructed mea- suring system which is capable of measuring the response and this system is then tested on provided samples.
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Investigation of spin dynamics in hybrid structures based on ferromagnetic semi-conductor (Ga,Mn)As
Butkovičová, Dagmar ; Němec, Petr (advisor) ; Hamrle, Jaroslav (referee) ; Žídek, Karel (referee)
Investigation of spin dynamics in hybrid structures based on ferromagnetic semi- conductor (Ga,Mn)As Abstract: This dissertation deals with the study of hybrid ferromagnet/semiconductor structures, which are of particular for spintronics. We focused on heterostructures that contain ferromagnetic semiconductor (Ga,Mn)As, which is the most studied model ma- terial from the group of diluted magnetic semiconductors. The main goal of this work was a detailed study of the Optical Spin Transfer Torque (OSTT) phenomenon, which is an optical equivalent of the STT effect, which is used in ferromagnetic metal layers for non-thermal switching of the direction of magnetization. In the first part of the work, we describe experiments aimed at achieving non-thermal control of the direction of mag- netization in (Ga,Mn)As with the contribution of control of magnetic anisotropy using mechanical strain induced by a piezo-transducer (PZT) in hybrid structure (Ga,Mn)As/GaAs/PZT. For this purpose, the preparation of the structure was first opti- mized, which was tested in detail by means of X-ray diffraction and magneto-optical methods. However, we were unable to achieve magnetization switching due to the OSTT phenomenon. In addition, we found that the results measured at low temperature are very poorly reproducible, despite...
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Investigation of spin polarization in semiconductors by laser spectroscopy
Butkovičová, Dagmar
This work is devoted to the investigation of a spin polarization in ferromagnetic semiconductor Ga1-xMnxAs with a broad nominal concentration of manganese ions using one method of the ultrafast laser spectroscopy - the time-resolved Kerr rotation. At first, the experimental setup was optimized for the investigation of the dynamics of spin polarized charge carriers in semiconductors which were photo-generated by circularly polarized laser pulses. It was observed that the measured signal is induced by spin-polarized electrons. Due to a small thickness of the investigated ferromagnetic films the measured signal probably monitored the dynamics of fotogenerated electrons in GaAs substrate. Nevertheless, the measured data show that the electron spin dynamics in the substrate is significantly influenced by proximity effect due to the deposited ferromagnetic layer.
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Spatially resolved measurements of magneto-optical Kerr effect in nanostructures
Kletečka, Vojtěch ; Veis, Martin (advisor) ; Butkovičová, Dagmar (referee)
With increasing complexity of devices utilizing magnetic properties of mate- rials grows the need to characterize and further examine these properties. One of the possible ways to do this is utilizing of magnetooptical Kerr effect with Kerr microscope. In the theoretical part of this thesis is at first described response of the electromagnetic wave to the magnetic field in reflection on the ferromagnetic material and then explained the possibility of using the effect in measurements of the response. After that in experimental part is designed and constructed mea- suring system which is capable of measuring the response and this system is then tested on provided samples.
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Investigation of spin polarization in semiconductors by laser spectroscopy
Butkovičová, Dagmar
This work is devoted to the investigation of a spin polarization in ferromagnetic semiconductor Ga1-xMnxAs with a broad nominal concentration of manganese ions using one method of the ultrafast laser spectroscopy - the time-resolved Kerr rotation. At first, the experimental setup was optimized for the investigation of the dynamics of spin polarized charge carriers in semiconductors which were photo-generated by circularly polarized laser pulses. It was observed that the measured signal is induced by spin-polarized electrons. Due to a small thickness of the investigated ferromagnetic films the measured signal probably monitored the dynamics of fotogenerated electrons in GaAs substrate. Nevertheless, the measured data show that the electron spin dynamics in the substrate is significantly influenced by proximity effect due to the deposited ferromagnetic layer.
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Modeling of optical bistability
Čerňanský, Robert ; Trojánek, František (advisor) ; Butkovičová, Dagmar (referee)
My work is dealing with nonlinear optical event called optical bistability or multistability which is expressed during an interaction of high-energetic laser beam with material. Optical bistability may occur in absortive coeficient or in refractive indice (or both). My work is more-less aimed as a theoretical experiment where I had predefined initial conditions and by the help of Microsoft Office Excel 2007 programm I have modeled the dispersive optical bistability for nanocrystalitc form of silicon dioxide and cadmium selenid. Powered by TCPDF (www.tcpdf.org)
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Investigation of spin polarization in semiconductors by laser spectroscopy
Butkovičová, Dagmar ; Němec, Petr (advisor) ; Kadlec, Filip (referee)
This work is devoted to the investigation of a spin polarization in ferromagnetic semiconductor Ga1-xMnxAs with a broad nominal concentration of manganese ions using one method of the ultrafast laser spectroscopy - the time-resolved Kerr rotation. At first, the experimental setup was optimized for the investigation of the dynamics of spin polarized charge carriers in semiconductors which were photo-generated by circularly polarized laser pulses. It was observed that the measured signal is induced by spin-polarized electrons. Due to a small thickness of the investigated ferromagnetic films the measured signal probably monitored the dynamics of fotogenerated electrons in GaAs substrate. Nevertheless, the measured data show that the electron spin dynamics in the substrate is significantly influenced by proximity effect due to the deposited ferromagnetic layer.
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