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The magnetocrystalline anizotropy in the TbTX compounds
Klicpera, Milan
Title: The magnetocrystalline anizotropy in the TbTX compounds Author: Milan Klicpera Department: Department of Condensed Matter Physics Supervisor: doc. Mgr. Pavel Javorský, Dr. Supervisor's e-mail address: javor@mag.mff.cuni.cz Abstract: The subject of this work is the study of structural, magnetic and trans- port properties of the TbNi(Al,In) series to finding connections between magne- tocrystalline anisotropy and lattice parameters of the structure of the TbTX com- pounds. Polycrystalline TbNiAl1−xInx samples were prepared by melting. The phase and crystal structure analysis were provided on samples. We performed the measurements of the magnetization, susceptibility, specific heat, resistivity, low temperature X-ray diffraction and powder neutron diffraction. From the neutron diffraction data we refined lattice parameters and propagation vectors of the series. The main propagation is (000) and second weaker component has the propagation vector (1 2 0 1 2 ). The change of the magnetocrystalline anisotropy from uniaxial to planar type occurs for compounds with x between 0.4 and 0.5. Keywords: magnetization, X-ray and neutron diffraction, electrical resistivity.
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Magnetokrystalová anizotropie ve sloučeninách TbTX
Klicpera, Milan ; Javorský, Pavel (advisor) ; Prokleška, Jan (referee)
Title: The magnetocrystalline anizotropy in the TbTX compounds Author: Milan Klicpera Department: Department of Condensed Matter Physics Supervisor: doc. Mgr. Pavel Javorský, Dr. Supervisor's e-mail address: javor@mag.mff.cuni.cz Abstract: The subject of this work is the study of structural, magnetic and trans- port properties of the TbNi(Al,In) series to finding connections between magne- tocrystalline anisotropy and lattice parameters of the structure of the TbTX com- pounds. Polycrystalline TbNiAl1−xInx samples were prepared by melting. The phase and crystal structure analysis were provided on samples. We performed the measurements of the magnetization, susceptibility, specific heat, resistivity, low temperature X-ray diffraction and powder neutron diffraction. From the neutron diffraction data we refined lattice parameters and propagation vectors of the series. The main propagation is (000) and second weaker component has the propagation vector (1 2 0 1 2 ). The change of the magnetocrystalline anisotropy from uniaxial to planar type occurs for compounds with x between 0.4 and 0.5. Keywords: magnetization, X-ray and neutron diffraction, electrical resistivity.
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Magnetism in transition metal oxides
Burianová, Simona ; Kalbáčová Vejpravová, Jana (advisor) ; Svoboda, Pavel (referee)
The CoFe2O4 nanocrystals are highly attractive due to their magnetic properties - large coercivity (up to 2 T at low temperatures) with moderate saturation magnetization (80 A.m2.kg-1), remarkable chemical stability and mechanical hardness. Upon RE doping, a significant change of the properties is expected. This thesis is focused on investigation of Co1-LaxFe2O4, x = 0.05 - 0.5 and CoLaxFe2-x O4 x = 0.05 - 0.2 nanoparticles prepared by sol-gel and microemulsion method, respectively, with varying particle size according to the final heat treatment. In the former case, the particles were embedded in amorphous SiO2 matrix, while in the latter case, the samples were matrix-free. The samples were characterized using X-ray diffraction and Mössbauer spectroscopy. Measurements of the temperature dependence of the ZFC-FC magnetization revealed that the blocking temperature is above the room temperature. The values of coercivity and saturation magnetization strongly depend on particles size determined by method of preparation. The higher coercivity values of about 2 T at 10 K show the samples prepared by the sol-gel method. The obtained results are discussed in the context of preparation method, particle size and level of La doping.
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Magnetic nanostructures with application potential
Bittová, Barbara ; Holý, Václav (referee) ; Kalbáčová Vejpravová, Jana (advisor)
The thesis is mainly focused on the investigation of macroscopic and microscopic magnetic properties of selected nanomaterials containing cobalt and iron, and also the capability of our new device, scanning probe microscope Multimode V by Veeco, to directly visualise morphology and magnetic structure of these samples (Magnetic Force Miscroscopy, MFM). Investigated materials, such as CoFe2O4 nanoparticles and SiO2_Co_Si(111) thin films and multilayers are in general promising materials in many fields. In the medicine, the nanoparticles are used as the drug targets or contrast agents whereas in electronics, the (nano)granular thin films are the starting point in fabrication of high density storage media. The macroscopic magnetic properties of our samples are discusses in a view of superparamagnetic phenomena. The interactions in systems of nanoparticles are presented theoretically within the up-to date knowledge and also experimentally by demonstrating the behavior of the strongly-interacting, uper-spin-glass system. The thin films are studied in term of their granular structure and magnetic anisotropy. The morphology and the microscopic domain structure, respectively, are studied with use of the MFM. The first successful results obtained in our lab by this method are presented.
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MRI Acquisition and Preprocessing of Image Sequences for Clinical Perfusion Imaging
Krchňavý, Jan ; Bartoš, Michal (referee) ; Jiřík, Radovan (advisor)
This thesis describes the theory for static and dynamic magnetic-resonance imaging using contrast agents affecting T1 relaxation time. The available acquisition methods in the specified facility of Masaryk Oncological Institute in Brno are described. The sequences for subsequent experimental measurements are selected. The used phantoms are described. Acquisition protocol for measuring is described briefly and the evaluation method for the measured data is suggested. The best acquisition sequence and a method of measurements is chosen influenced by estimation of relaxation time T1, sensitivity and signal to noise ratio. Perfusion analysis is executed and perfusion parameters are calculated. The work was supported by the European Regional Development Fund and the State Budget of the Czech Republic (RECAMO, CZ.1.05/2.1.00/03.0101).
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