National Repository of Grey Literature 77 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Magneto-optical study of antiferromagnetic materials for spintronics
Kubaščík, Peter ; Němec, Petr (advisor) ; Výborný, Karel (referee)
The main goal of this thesis was to develop an experimental technique for investigation of ferromagnetic and antiferromagnetic materials using magneto-optical effects that are quadratic in magnetization. Using a prototype of 2-dimensional electromagnet, which enables to rotate magnetic field of constant magnitude in the sample plane, we were able to study spectral dependences and anisotropies of corresponding magneto-optical coefficients. In ferromagnetic semiconductor GaMnAs we revealed that the anisotropy of Voigt effect magneto-optical coefficient is strongly wavelength dependent - this coefficient can be both isotropic and anisotropic. Very strong anisotropy of this coefficient was observed for metallic FeRh in a ferromagnetic state. Finally, a new method that can be used to measure Voigt effect in antiferromagnetic state of FeRh was demonstrated.
Inverter for DC motor 800 W
Němec, Petr ; Toman, Marek (referee) ; Procházka, Petr (advisor)
The goal of this Bachelor´s thesis is design of an power inverter for BDC motor 36 V/800 W with permanent magnets. The first part of this work is devoted to the brief description of drive elements, which with designed converter create drive system. It´s also contain measures of used BDC motor MY1020. In the second part there is a outline description of functions and connection of DC/DC converters with respect to the final solution. The power circuit will be built with the MOS-FET IRFP4110 connected to the H bridge. Transducer control logic will be provided by the microcontroller development board Arduino UNO 3 with the integrated driver circuit IR2110.
Investigation of electrical conductivity of thin films under influence of mechanical strain
Farkaš, Andrej ; Němec, Petr (advisor) ; Voves, Jan (referee)
Magnetization of atiferromagnetic devices can be manipulated electrically or mechanically. In order to do mechanical manipulation specialized device was constructed and tested with cross structure on three different thin metal layers comparable to antiferromagnetic devices on top of the most common substrates GaAs and GaP. Results of said testing proved machine is usable for intended purpose, with few tweaks.
Optical spectroscopy of antiferromagnets
Kimák, Jozef ; Němec, Petr (advisor) ; Tesařová, Naďa (referee)
Antiferromagnets, magnetically ordered materials without macroscopic magnetization, are rather difficult to study by conventional magnetic characterization tools. This thesis was focus on optical research of antiferromagnets. We studied in detail magneto-optical effects quadratic in magnetization, magnetic linear dichroism and Voigt effect, that are present even in compensated antiferromagnets. We studied magnetic semiconductor (Ga,Mn)As where these effects are rather pronounced and by employing a 2-dimensional electromagnet, we demonstrated that these effects can be used for a determination of magnetic and magneto-optical anisotropy in investigated materials. Alternative approach was used in a thin film made from a non-collinear antiferromagnet Mn3NiN where we studied changes of optical and magneto-optical properties. We revealed that they are strongly affected by the strain connected with the temperature-induced phase transition in the STO substrate. This demonstrates that optical spectroscopy can be used for the research of antiferromagnets quite efficiently.
Ultrafast laser spectroscopy of antiferromagnets
Saidl, Vít ; Němec, Petr (advisor) ; Kužel, Petr (referee) ; Hamrle, Jaroslav (referee)
This work is dedicated to the study of two antiferromagnetic materials that are suitable for use in spintronic devices. In series of FeRh samples we studied the transition temperature between the antiferromagnetic and ferromagnetic phases. We developed a method based on material optical response for a quick determination of this temperature, which enabled us to study with a spatial resolution of 1 μm a magnetic inhomogeneity of prepared samples.We also developed a method for a determination of the Néel temperature and the magnetization easy axis position in thin films prepared from compensated antiferromagnetic metal. We successfully applied this method on an uniaxial sample of CuMnAs and we discussed its applicability for a research of samples with a biaxial magnetic anisotropy.
Construction of laser scanning magneto-optical microscope
Betušiak, Marián ; Němec, Petr (advisor) ; Beran, Lukáš (referee)
Title: Construction of laser scanning magneto-optical microscope Author: Marián Betušiak Department: Department of Chemical Physics and Optics Supervisor: prof. RNDr. Petr Němec, Ph.D., Department of Chemical Physics and Optics Abstract: The main goal of this thesis was to build a scanning magneto-optical microscope in the newly established Magneto-optical laboratory at the Department of Chemical Physics and Optics and particularly to compare different techniques for detection of magneto-optical (MO) signals. During the preparation stages, we first simulated the signal detected in different optical arrangements using Jones matrix formalism. Subsequently, we verified the functionality of the constructed microscope using a ferromagnetic sample of YIG:Pr and we compared experimentally different methods of the MO signal detection. Obtained experimental results are in perfect qualitative agreement with the predictions of Jones theory. Keywords: scanning magneto-optical microscope, Kerr effect, magnetic domains
Magneto-optical characterization of spintronic materials
Wohlrath, Vladislav ; Němec, Petr (advisor) ; Olejník, Kamil (referee)
This work deals with magneto-optical measurements using a recently built prototype of a two- dimensional electromagnet. In the first stage, an experimental setup for magneto-optical measurements was constructed, which enables to study Voigt effect and magnetic linear dichroism. In the second stage, this setup was tested by measuring hysteresis loops in a sample of ferromagnetic semiconductor GaMnAs. In the final stage, we performed a new type of magneto- optical experiments, which fully exploits the two-dimensional control of the magnetic field generated in the electromagnet.
The Fair and True View of Business Unit in the Financial Statements
Němec, Petr ; Ondroušková, Renata (referee) ; Fedorová, Anna (advisor)
The diploma thesis deals with the issue of the fair and true view of business unit in the financial statements. The basic statements of the financial statements comprise the balance sheet, the profit and loss statement and the annexe to the financial statements explaining methods used for accounting of the accounting cases. The practical part of the diploma thesis is focused on analysis of the financial statements of particular entity and applied accounting procedures. The analysis of this unit was carried out focusing on achievement of fair and true view of this unit in the financial statements. The financial position and performance of the selected business unit was evaluated on the basis of selected financial indicators according to the unit's data and its own calculations. The results were compared and evaluated.
Characterization of two-dimensional electromagnet
Kimák, Jozef ; Němec, Petr (advisor) ; Olejník, Kamil (referee)
Abstract:In this work we studied magnetic field magnitude and direction ge- nerated by a prototype of 2-dimensional electromagnet, which was recently cons- tructed in Laboratory of the OptoSpintronics. This electromagnet is formed by two pairs of coils with a mutually perpendicular position of their poles. In parti- cular, we revealed that, by appropriately setting the current through the coils, it is possible to rotate reproducibly the field direction in the plane of the poles for the field magnitude of about 200 mT. We also observed that the generated field is rather homogeneous in a region with a radius of about 5 mm, which corresponds to a typical sample size. On the other hand, the functionality of the electromag- net at lower fields could not be tested unambiguously due to technical problems with a home-made detection Hall probes. This problem will be addressed in the following work. 1
Optical spectroscopy of magnetically ordered materials
Surýnek, Miloslav ; Němec, Petr (advisor) ; Němec, Hynek (referee)
Spintronics is a dynamically developing branch of electronics which for transfer, processing and storing of information use not only electron charge but also its spin. Materials appropriate for a construction of spintronic devices should sustain the spin order for a sufficiently long time enabling a manipulation of spins. Simultaneously, in these materials the spin of electrons should be possible to transport fast and long enough across the device. In this work, heterostructure of GaAs/AlGaAs fulfilling these requirements is investigated by a pump-probe technique. In particular, long spin lifetimes of electrons in the heterostructure are studied using the resonant spin amplification method and with a use of the pulse picker. The nuclear spin polarization and the effect of an applied electric current on the studied heterostructure are also investigated in this work. Spectral filters are used to improve the existing experimental setup for the pump-probe technique and to measure a magnetooptical spectrum of the investigated heterostructure.

National Repository of Grey Literature : 77 records found   1 - 10nextend  jump to record:
See also: similar author names
18 NĚMEC, Pavel
30 NĚMEC, Petr
1 Němec, P.
18 Němec, Pavel
1 Němec, Přemysl
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