Studium fyzikálních vlastností Heuslerových slitin

Diplomová práce je věnována systematickému studiu strukturních trans- formací Heuslerových slitin pomocí spektroskopické elipsometrie a magne- tooptické speltroskopie. Strukturní transformace v těchto slitinách jsou vyvolány rozdílnými mikroskopickými mechanismy. Experimentální data získaná v této práci byla konfrontována s výsledky teoretických modelů. To umožnilo diskutovat získané výsledky a navrhnout jejich vysvětlení. V případě slitin Co-Fe-Si byla pozorována změna optických i magneooptických vlastností v závislosti koncetraci železa. Toto bylo vysvětleno zmenšováním zakázaného pásu minoritních spinů se vzrůstajícím podílem Fe. Teplotní závislost optických a magnetooptických vlastností slitiny Ni-Mn-Ga jasně prokázala existenci tzv. Martensitické transformace z kubické do tetragonální fáze. Studium slitin Rh-Mn-Co-Sn neprokázalo jasnou závislost fyzikálních vlastností na koncetraci Rh a Mn. To bylo vysvětleno značným pnutím ve vzorcích, které zkreslilo měřená data. 1This diploma thesis is devoted to systematic study of structural trans- formations of Heusler alloys by means of spectroscopic ellipsometry and magneto-optical spectroscopy. Structural transformations in these alloys are induced by different microscopic mechanisms. Obtained experimental results were confronted with theoretical calculations. This allowed the discussion of obtained results and suggestion of their interpretation. In the case of Co- Fe-Si alloys, changes in optical and magneto-optical properties with change of Co-Fe ratio were observer. This was explained by lowering of the gap for minority spins with increasing Fe concentrations. Temperature dependent optical and magneto-optical properties of Ni-Mn-Ga alloy showed the pres- ence of so-called Martensitic transformation from cubic to tetragonal phase. A study of Mn-Rh-Co-Sn alloys did not show a clear dependence of physical properties upon the concentration of Rh and Mn. This was explained by strong strain inside the samples, which distorted obtained results. 1Institute of Physics of Charles UniversityFyzikální ústav UKFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Studium fyzikálních vlastností Heuslerových slitin

Diplomová práce je věnována systematickému studiu strukturních trans- formací Heuslerových slitin pomocí spektroskopické elipsometrie a magne- tooptické speltroskopie. Strukturní transformace v těchto slitinách jsou vyvolány rozdílnými mikroskopickými mechanismy. Experimentální data získaná v této práci byla konfrontována s výsledky teoretických modelů. To umožnilo diskutovat získané výsledky a navrhnout jejich vysvětlení. V případě slitin Co-Fe-Si byla pozorována změna optických i magneooptických vlastností v závislosti koncetraci železa. Toto bylo vysvětleno zmenšováním zakázaného pásu minoritních spinů se vzrůstajícím podílem Fe. Teplotní závislost optických a magnetooptických vlastností slitiny Ni-Mn-Ga jasně prokázala existenci tzv. Martensitické transformace z kubické do tetragonální fáze. Studium slitin Rh-Mn-Co-Sn neprokázalo jasnou závislost fyzikálních vlastností na koncetraci Rh a Mn. To bylo vysvětleno značným pnutím ve vzorcích, které zkreslilo měřená data. 1This diploma thesis is devoted to systematic study of structural trans- formations of Heusler alloys by means of spectroscopic ellipsometry and magneto-optical spectroscopy. Structural transformations in these alloys are induced by different microscopic mechanisms. Obtained experimental results were confronted with theoretical calculations. This allowed the discussion of obtained results and suggestion of their interpretation. In the case of Co- Fe-Si alloys, changes in optical and magneto-optical properties with change of Co-Fe ratio were observer. This was explained by lowering of the gap for minority spins with increasing Fe concentrations. Temperature dependent optical and magneto-optical properties of Ni-Mn-Ga alloy showed the pres- ence of so-called Martensitic transformation from cubic to tetragonal phase. A study of Mn-Rh-Co-Sn alloys did not show a clear dependence of physical properties upon the concentration of Rh and Mn. This was explained by strong strain inside the samples, which distorted obtained results. 1Fyzikální ústav UKInstitute of Physics of Charles UniversityFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Studie optických a magnetooptických vlastností ferrimagnetických granátů pro fotonické a spintronické aplikace

Název práce: Studie optických a magnetooptických vlastností ferrimagnetických granátů pro fotonické a spintronické aplikace Autor: RNDr. Lukáš Beran Katedra: Fyzikální ústav Univerzity Karlovy Vedoucí disertační práce: RNDr. Martin Veis, PhD., Fyzikální ústav Univerzity Karlovy Abstrakt: Tato doktorská práce se věnuje přípravě a systematické charakterizaci fyzikálních vlastností tenkých vrstev železitých granátů s potenciálním využitím ve fotonických a spintronických zařízeních. Zkoumané vzorky byly připraveny pomocí metalo-organické dekompozice a pulzní laserové depozice. Studie se zaměřila na strukturní a magnetickou charakterizaci spolu s optickými a mag- netooptickými vlastnostmi. Získané experimentální výsledky byly dále srovnány s teoretickými výpočty. Aplikační potenciál granátů pro fotonická zařízení byly diskutovány na základě určeného faktoru jakosti (Figure of Merit). Vysoké hod- noty byly dosaženy pro monokrystalácké filmy Ce dopovaného yttritého železitého granátu a polykrystalické vrstvy Bi dopovaného yttritého železitého granátu na křemíkovém substrátu. Dále byly připraveny vrstvy nových granátů vzácných zemin se snahou dosáhnout kolmé magnetické anizotropie. To se podařilo pro tři...Title: Optical and magneto-optical studies of ferrimagnetic garnets for photonic and spintronic applications Author: RNDr. Lukáš Beran Department: Intitute of Physics of Charles University Supervisor: RNDr. Martin Veis, PhD., Institute of Physics of Charles University Abstract: This doctoral thesis is devoted to fabrication and systematic char- acterization of physical properties of thin films of iron garnets with potential applications in photonic and spintronic devices. Investigated samples were pre- pared by metallo-organic decomposition and pulsed laser deposition. The study was focused on structural and magnetic characterizaiton along with optical and magneto-optical properties. Obtained experimental results were further con- fronted with theoretical calculations. The application potencial of garnets for photonic devices was discussed based on determined Figure of Merit (Faraday rotation to optical loss ratio). High values were achieved for single crystal thin film of Ce doped yttrium iron garnet on galium gadolinium garnet substrate as well as for pollycrystalline Bi doped yttrium iron garned on silicon substrate. Furthermore, new rare-earth garnets were prepared with attempt to achieve per- pendicular magnetic anisotropy of these film. This was achieved for three di erent materials, which were not...Fyzikální ústav UKInstitute of Physics of Charles UniversityMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Utjecaj rednog broja laktacije na omjer važnih zdravih masnih kiselina u sirovom mlijeku krava holstein pasmine

The objective of this study was to determine and evaluate the effect of parity on the fatty acids groups’ proportion in Holstein cows’ milk during the first phase of lactations, with an emphasis on its potential importance for consumer health. A total of 25 Holstein cows, 9 primiparous, 9 in the 2nd, and 7 in the 3rd and subsequent parity, were observed and sampled at 7-day intervals through the first 17 weeks of lactation. The percentage proportion of saturated (hypercholesterolemic and volatile as its components) and unsaturated (monounsaturated and polyunsaturated as its components) fatty acids in the samples of milk fat (n=425) was determined. The effects of parity and negative energy balance, as well as regression, on the lactation week and the fat to protein ratio were evaluated using SAS 9.3. A significantly (P<0.01) lower proportion of unhealthy hypercholesterolemic fatty acids was detected in primiparous cows (-2.67 %) and those in the 3rd and subsequent lactation (-2.94 %) compared to the 2nd lactation, as well as a simultaneously higher proportion of healthy unsaturated fatty acids (+2.07, respectively +3.08 %). The determined relationships corresponded to organism stress evoked by the initiation of milk production and its maintenance in higher parities. Therefore, the generally required prolongation of dairy cows’ longevity can influence on the quality of raw milk, especially considering composition of fatty acids.Cilj ovog istraživanja bio je utvrditi i procijeniti utjecaj rednog broja laktacije na udio pojedinih skupina masnih kiselina, u mlijeku holstein krava tijekom prve faze laktacije, s naglaskom na njihovu potencijalnu važnost za zdravlje potrošača. Ukupno 25 holstein krava, devet prvotelkinja, devet u drugoj, i sedam u trećoj i naknadnim laktacijama, promatrane su i uzorkovane u sedmodnevnim intervalima tijekom prvih 17 tjedana laktacije. Utvrđivan je udio zasićenih (unutar te skupine hiperkolesterolemičnih i hlapivih masnih kiselina) te nezasićenih (unutar te skupine mononezasićenih i polinezasićenih) masnih kiselina u uzorcima mliječne masti (n=425). Utjecaj rednog broja laktacije i negativne energetske bilance, kao i regresija, na tjedne laktacije i omjer masti i proteina procijenjeni su pomoću SAS 9.3. Značajno (P<0,01) manji udio po zdravlje nepovoljnih hiperkolesterolemičnih masnih kiselina utvrđen je u prvotelkinja (-2,67 %) i onih u 3. i naknadnim laktacijama (-2,94 %) u odnosu na krave u drugoj laktaciji, kao i istodobno veći udio po zdravlje povoljnih nezasićenih masnih kiselina (2,07 %, odnosno 3,08 %). Utvrđena veza objašnjava se stresom organizma prouzrokovanim početkom proizvodnje mlijeka i održavanjem te proizvodnje tijekom kasnijih laktacija. Dakle, općenito dulji životni vijek mliječnih krava može utjecati na kvalitetu sirovog mlijeka, osobito s obzirom na sastav masnih kiselina

Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

Magneto-optical cerium-substituted yttrium iron garnet (Ce:YIG) thin films display Faraday and Kerr rotation (rotation of light polarisation upon transmission and reflection, respectively) as well as a nonreciprocal phase shift due to their non-zero off-diagonal permittivity tensor elements, and also possess low optical absorption in the near-infrared. These properties make Ce:YIG useful in providing nonreciprocal light propagation in integrated photonic circuits, which is essential for accomplishing energy-efficient photonic computation and data transport architectures. In this study, 80 nm-thick Ce:YIG films were grown on Gadolinium Gallium Garnet substrates with (100), (110) and (111) orientations using pulsed laser deposition. The films had bulk-like structural and magnetic quality. Faraday and Kerr spectroscopies along with spectroscopic ellipsometry were used to deduce the complete permittivity tensor of the films in the ultraviolet, visible and near-infrared spectral region, and the magneto-optical figure of merit as a function of wavelength was determined. The samples showed the highest IR Faraday rotation reported for thin films of Ce:YIG, which indicates the importance of this material in development of nonreciprocal photonic devices.National Science Foundation (U.S.)Semiconductor Research Corporation. Function Accelerated nanoMaterial Engineerin

BEER - The Beamline for European Materials Engineering Research at the ESS

The Beamline for European Materials Engineering Research (BEER) will be built at the European Spallation Source (ESS). The diffractometer utilizes the high brilliance of the long-pulse neutron source and offers high instrument flexibility. It includes a novel chopper technique that extracts several short pulses out of the long pulse, leading to substantial intensity gain of up to an order of magnitude compared to pulse shaping methods for materials with high crystal symmetry. This intensity gain is achieved without compromising resolution. Materials of lower crystal symmetry or multi-phase materials will be investigated by additional pulse shaping methods. The different chopper set-ups and advanced beam extracting techniques offer an extremely broad intensity/resolution range. Furthermore, BEER offers an option of simultaneous SANS or imaging measurements without compromising diffraction investigations. This flexibility opens up new possibilities for in-situ experiments studying materials processing and performance under operation conditions. To fulfil this task, advanced sample environments, dedicated to thermo-mechanical processing, are foreseen

Magnetic and Magneto-Optical Properties of Fe75-xMn25Gax Heusler-like Compounds

Fe75-xMn25Gax Heusler-like compounds were investigated in a wide range of Fe/Ga ratios while keeping the Mn content constant and equal 25 at% in order to elucidate the interplay between magnetic properties and composition. Materials were prepared by arc-melting from pure elements and subsequently annealed. Experimental investigations were focused on magnetization behavior in a wide temperature range from 4 to 1000 K and magnetic field up to 9 T. Optical and magneto-optical (MO) measurements were employed to shed more light on the magnetic state and electronic structure of investigated materials. Magnetization measurements indicated that in the vicinity of stoichiometry (Fe2MnGa) the compounds are ferro/ferrimagnetic, whereas the Fe-deficient compound is paramagnetic and at high Fe concentration the antiferromagnetic interaction prevails. Theoretical calculations of corresponding ordered and disordered stoichiometric compounds were carried out and compared to the experiment on the level of net magnetic moment as well as magneto-optical spectra. This comparison suggests that the Heusler crystal structure, L2(1), is not present even close to stoichiometry. Moreover, the comparison of density of states (DOS) for ordered and disordered structures allowed us to explain missing martensitic transformation (MT) in investigated materials

The instrument suite of the European Spallation Source

An overview is provided of the 15 neutron beam instruments making up the initial instrument suite of the European Spallation Source (ESS), and being made available to the neutron user community. The ESS neutron source consists of a high-power accelerator and target station, providing a unique long-pulse time structure of slow neutrons. The design considerations behind the time structure, moderator geometry and instrument layout are presented. The 15-instrument suite consists of two small-angle instruments, two reflectometers, an imaging beamline, two single-crystal diffractometers; one for macromolecular crystallography and one for magnetism, two powder diffractometers, and an engineering diffractometer, as well as an array of five inelastic instruments comprising two chopper spectrometers, an inverse-geometry single-crystal excitations spectrometer, an instrument for vibrational spectroscopy and a high-resolution backscattering spectrometer. The conceptual design, performance and scientific drivers of each of these instruments are described. All of the instruments are designed to provide breakthrough new scientific capability, not currently available at existing facilities, building on the inherent strengths of the ESS long-pulse neutron source of high flux, flexible resolution and large bandwidth. Each of them is predicted to provide world-leading performance at an accelerator power of 2 MW. This technical capability translates into a very broad range of scientific capabilities. The composition of the instrument suite has been chosen to maximise the breadth and depth of the scientific impact o

Measurement of the optical properties of display devices with a digital camera

V práci je řešena problematika automatizace měření optických vlastností zobrazovacích zařízení digitálním fotoaparátem a jejich vyhodnocení. Digitální fotoaparát může najednou zachytit celé zobrazovací zařízení a proto je tato metoda rychlejší než ostatní dostupné metody. V případě, že chceme změřit optické vlastnosti daného zobrazovacího zařízení, můžeme využít klasickou metodu měření parametrů obrazu pomoci sondy pro kalibraci zobrazovacích zařízení. Ovšem tato metoda je časově náročná, jelikož je zapotřebí sondou měřit ve více bodech na zobrazovacím zařízení a následně naměřená data zpracovat. Pro automatizací měření a vyhodnocení můžeme využít kvalitní digitální fotoaparát, který umožňuje analyzovat nezpracovaná data snímaná přímo snímacím prvkem fotoaparátu. Tato data se na základě známých parametrů expozice dají přepočítat na jas a z něj pak vyjádřit potřebné optické parametry, např. kontrast a rovnoměrnost rozložení jasu. Cílem této práce je automatizovat proces snímání zobrazovacího zařízení pomocí digitálního fotoaparátu Nikon D7100, zpracování pořízených snímků za účelem vypočtu jasů potřebných ploch a získat základní parametry testovaného zobrazovacího zařízení (například kontrast, jas, rovnoměrnost jasu). Výsledek této práce může být využit například pro automatizaci a zrychlení výstupní kontroly zobrazovacích zařízení v průmyslové výrobě.ObhájenoThis paper deals with the automatization measurement of the optical properties of the display devices with a digital camera. Because the digital camera can capture the entire screen at one time, makes it faster than other available methods. If test optical properties display devices are required, it is possible to use calibration sensor. However, this method is slow, because it is necessary with the calibration probe measure multiple points on the display device and then the measured data are processed. For automation of the measurement and evaluation can be used high quality digital camera that allows to analyse raw data. These data are converted based on exposure parameters and then it is possible to check these parameters displayed device brightness, contrast or distribution of brightness from the captured images. The aim of this paper is to automate the process of capturing a display device using a digital camera Nikon D7100 and afterwards, these captured images are used to evaluate and check the basic parameters of the test display devices such as, contrast, brightness, contrast or distribution of brightness. The result of this work can be used, for example, to automate and accelerate output control display devices in industrial production

Design of a poster

Série obsahuje jedenáct plakátů na sociální téma. Cílem bylo vytvořit konsistentní sérii, přestože každý z plakátů řeší jiné téma ze sociální oblasti. Jsou zde plakáty o pedofilii, prostituci, násilí na ženách, toleranci homosexuálů, Facebooku, komunikaci a Evropské unii.Všechny plakáty používají pouze červenou, modrou, černou nebo bílou barvu. Celá série je vytvořena pomocí vektorové grafiky.Oddělení designuObhájenoThe series of posters includes eleven posters with social theme. The aim was to create a consistent set, but each poster deals with slightly different topic. There are posters about pedophilia, prostitution, violence against women, toleration of homosexuals, Facebook, communication and European Union. All posters are only in red, blue, black and white colour. The whole art work is made in vector graphics