National Repository of Grey Literature 73 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Design of Optically Detected Magnetic Resonance (ODMR) Spectrometer
Schneider, Martin ; Veis, Martin (referee) ; Neugebauer, Petr (advisor)
Diplomová práce se zabývá návrhem a sestavením nového spektrometru opticky detekované magnetické rezonance (ODMR) modifikací stávajícího spektrometru magnetického kruhového dichroismu (MCD) přivedením mikrovlnného ozařování. Je navrhnut nový držák vzorku umožnující osvětlení jak viditelným světlem, tak mikrovlnným zářením. Pro přivedení vlnění o nižších frekvencích je navržena anténa, určená k umístění pod vzorkem. Schopnosti celého systému jsou demonstrovány na sloučenínách kovových komplexů.
Mapping of changes in optical and magneto-optical responses of Ni-Mn-Ga thin films across martensitic transformation and strain relaxation
Makeš, Matěj ; Veis, Martin (advisor) ; Zemen, Jan (referee)
This thesis studies optical and magneto-optical responses of thin epitaxial Ni-Mn- Ga films prepared by magnetron sputtering. The relative permittivity tensor spectra were computed from the spectroscopic ellipsometry data measured both without the external magnetic field and in the out-of-plane magnetic field configuration. For one of the thin film samples, measurements across martensitic transformation were performed and temperature-hysteresis was observed. The analysis of the obtained spectra for thickness- varied series of samples clearly demonstrated the influence of substrate-induced strain and revealed a strong correlation between the out-of-plane lattice parameter and the properties of the obtained spectra. 1
Optical and magneto-optical properties of topological and Dirac materials
Tikuišis, Kristupas Kazimieras ; Veis, Martin (advisor) ; Slobodeniuk, Artur (referee) ; Erlingsson, Sigurdur Ingi (referee)
Kristupas Kazimieras Tikuišis, Department of Optoelectronics and Magneto- optics, Institute of Physics of Charles University Doctoral thesis: Optical and magneto-optical properties of topological and Dirac materials Supervisor: RNDr. Martin Veis, Ph.D., Department of Optoelectronics and Magneto-optics Advisers: RNDr. Roman Antoš, Ph.D., Department of Optoelectronics and Magneto-optics; Milan Orlita, Ph.D., National Laboratory of High Magnetic Fields LNCMI - Grenoble, CNRS (France) Abstract: Dirac materials exhibit unusual properties that attract interest both for practi- cal applications and fundamental reseach of exotic and relativistic physics. This thesis aims to systematically study basic optical and magneto-optical proper- ties of several members of these materials, namely the lead tin salts crystalline topological insulators and graphene. Non-destructive experimental techniques of spectroscoipic ellipsometry and FTIR magneto-optical spectroscopy were used to perform measurements from IR to UV spectral regions. A four-band Hamilto- nian model was derived to describe the most important band structure features of PbSnSe system placed in a magnetic field. This allowed to extract the band structure and topological parameters of the investigated samples. Extensive mod- eling results based on...
Magnetooptické studium vlivu zárodečné vrstvy na formování magnetických vlastností tenkých vrstev La2/3Sr1/3MnO3
Melzer, Aleš ; Veis, Martin (advisor) ; Zahradník, Martin (referee)
The impact of film thickness on optical and magneto-optical properties of La2/3Sr1/3O3 (LSMO) thin films was studied by optical and magneto-optical methods. A series of LSMO samples with increasing thicknesses was pre- pared by pulsed laser deposition on a silicon substrate with a Ca2Nb3O10 seed layer. The topology of both the substrates and the deposited films was examined by atomic force microscopy. The samples were subsequently analy- sed by spectroscopic ellipsometry and magneto-optical spectroscopy. The off- diagonal elements of the permittivity tensor of each layer were afterwards de- termined numerically from these measurements. The obtained spectra exhibi- ted spectroscopic structures found in epitaxial LSMO films grown on SrTiO3 (STO), reflecting good crystalline quality of investigated samples. Effects re- lated to gradual strain relaxation with increasing film thickness were observed on the spectra.
FDTD simulace funčkních fotonických struktur
Novák, Ondřej ; Veis, Martin (advisor)
This thesis aims to (i) design and optimize the geometry of magneto-photonic crystal based on ferromagnetic garnet in order to resonantly enhance the magneto-optical re- sponse, (ii) to explore the possibility of using magnetic shape memory alloy to build an optically active photonic element, using advanced FDTD modeling. A Faraday rotation of 180◦ was reached but with low values of transmissivity. An investigation of the origin of such high values of Faraday rotation led to a conclusion that such structure has to be highly sensitive towards a change of a refractive index of its surroundings. This was confirmed, and so further development of this structure can lead to an efficient concentra- tion detector. Three designs of optically active element utilizing deformation of magnetic shape memory material in the external magnetic field were numerically simulated. Two designs (photonic crystal with cylindric holes in a hexagonal lattice and self-standing foil with cylindric holes in a square lattice) proved to be efficient and worth of further development. 1
Kontrola magnetické anizotropie v multivrstvách Pt/Co/Pt
Nowak, Lukáš ; Veis, Martin (advisor)
This thesis aims to explore the effect of in situ ion gun etching on magnetic proper- ties, such as perpendicular magnetic anisotropy, of Pt/Co/Pt multilayers. Perpendicular magnetic anisotropy is of interest due to its importance in spintronic application. Calibration spectroscopic ellipsometry measurements of Pt and Co layers to obtain sputter yields of respective magnetron targets were performed as a first step. After that, ten Pt/Co/Pt multilayers with different Co and top Pt layer thicknesses were prepared. Five of these samples were etched by the ion gun, mounted inside of the magnetron chamber, during different stages of the deposition. To characterize the prepared samples, experimental and modeled Kerr rotation spectra were confronted. This provided an insight into the cross-sections of the investigated samples. Magnetic hysteresis loops measured by vibrating sample magnetometer and Kerr rotation setup demonstrated higher coercive field and change of the slope of the loop induced by ion etching. When compared to the obtained cross-sections, a correlation between the change of magnetic loops and intermixing of Pt and Co at the interface was visible. This intermixing was higher in samples treated by the ion gun. 1
Spectroscopic studies of new generation of optical and magneto-optical materials
Butková, Eva ; Veis, Martin (advisor) ; Chlan, Vojtěch (referee) ; Zemen, Jan (referee)
Title: Spectroscopic studies of new generation of optical and magneto-optical materials Author: Eva Butková Department / Institute: Institute of Physics of Charles University. Department of Materials Science and Technology of Nagaoka University of Technology. Supervisors of the doctoral thesis: RNDr. Martin Veis, Ph.D., Division of Magneto-optics, Institute of Physics of Charles University Dr. Takayuki Ishibashi, Ph.D., Department of Materials Science and Technology, Nagaoka University of Technology Abstract: In recent years, novel optical and magneto-optical devices have been proposed. This ranges from integrated photonic devices such as 3D holographic displays to magnetic recording, non- reciprocal photonic devices such as optical isolators and circulators or high-energy X-ray/gamma ray detectors. These devices, however, require suitable materials with tunable optical and magneto-optical properties. Presented thesis aims to systematically study such materials, namely GdxFe(100-x), magnetic garnets (Y3-xBixFe5O12, Nd2BiFe(5-x)GaxO12, Nd0.5Bi2.5Fe(5-x)GaxO12) and Ce(0.95-x)HfxCo0.05O(2-δ). Systematic study is carried out by the combination of experimental methods of spectroscopic ellipsometry, magneto-optical Kerr effect spectroscopy and Faraday effect spectroscopy. Experimental data are confronted to...
Physical properties of doped and non-doped Tb3Fe5O12 studied by optical spectroscopies
Vančík, Michal ; Veis, Martin (advisor) ; Mistrík, Jan (referee)
This thesis focuses on systematic study of optical and magneto-optical properties of non-doped and doped Tb3Fe5O12 thin films, on gadolinium gallium garnet and silicon substrates. Spectroscopic ellipsometry measurements were performed to obtain optical properties, thicknesses and surface roughness values of studied samples. The magneto- optical properties were investigated using the Kerr and Faraday effect measurements. Obtained experimental data were used to calculate the spectral dependence of the off- diagonal components of permittivity tensor. The results were compared with literature, and the effect of doping was discussed. On three samples, the spectral magneto-optical Kerr rotation hysteresis loops were measured, for the purpose of separating the individual contributions of sublattices. The analysis revealed that the method is probably insensitive to sublattice contributions but is sensitive to the contributions of regions with different magnetic anisotropy within the deposited layer. 1
Substrátem kontrolované fyzikální vlastnosti tenkých vrstev magnetických oxidů pro spintronické aplikace
Maleček, Tomáš ; Veis, Martin (advisor) ; Václavková, Diana (referee)
As conventional electronics approaches its fundamental limits, new paradigms are re- quired. Integration of new spintronic materials with current silicon technology shows great promise. This thesis demonstrates the possibility of growing textured stress-free La2/3Sr1/3MnO3 (LSMO) thin films on silicon with properties comparable to epitaxi- ally grown layers on SrTiO3 (STO). Growth of LSMO is achieved by a two-dimensional nanosheet (NS) seed layer of Ca2Nb3O10 inducing epitaxial stabilization of LSMO films. Samples of LSMO on NS/Si, prepared by pulsed laser deposition, have been shown to have lower magnetization than samples of LSMO on STO yet also possess a higher Curie temperature by more than 10 K. Spectral dependence of the full permittivity tensor was calculated from optical and magneto-optical measurements. Spectra of the off-diagonal element have been fitted with three diamagnetic transitions located around 1.9, 2.9 and 3.5 eV for samples on NS/Si as well as for samples on STO. Similarities between the samples open the possibility of integration of LSMO into silicon technology using NS. Temperature-dependent optical and magneto-optical properties of a sample of LSMO on STO have been evaluated.
Magneto-optical properties of ferrimagnetic garnet thin films with perpendicular magnetic anisotropy
Šetina, Jan ; Veis, Martin (advisor) ; Zázvorka, Jakub (referee)
The aim of this bachelor thesis is to optically and magnetooptically characterize terbium iron garnet and determine its compensation temperature. Another goal is to study magnetooptical response of bismuth doped iron garnets. This analysis was done by magnetooptical spectroscopy, which is suitable for study of thin films due to its high sensitivity and contactlessness. The experimental setup, which allows temperature dependent magnetooptical measurements, was developed and used in the thesis. The spectra of optical constants were deduced using spectroscopic ellipsometer. Hysteresis loop and Faraday rotation was measured on selected sample. These measurements provided new interesting insights in the materials properties, which are discussed in this thesis. 1

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1 VEIS, Miroslav
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