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Study of martensitic tranformation in Co doped NiMnGa films by optical and magnetooptical methods
Nowak, Lukáš ; Veis, Martin (advisor) ; Hamrle, Jaroslav (referee)
Martenzitic transformation is responsible for multiferroic behaviour of mag- netic shape memory effect. However, the origin of the transformation is not yet fully understood. Magnetic shape memory materials in general offer broad spectrum of possible applications. NiMnGa is the prototype compound of these materials. Particular changes in the electronic structure are the origin of marten- zitic transformation which is the key to magnetic shape memory effect. There- fore, the optical and magneto-optical methods are the ideal tools for its analysis. Studied samples were prepared using magnetron sputtering on MgO substrate. Measurements of the Kerr effect at polar configuration and normal light in- cidence were done using rotating analyzer method. Experimental results, in- cluding spectral ellipsometry and temperature dependent measurements, were compared with theoretical models and then discussed. 1
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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.
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Study of novel materials and nanostructures for spin photonics and electronics
Pavelka, Martin ; Veis, Martin (advisor) ; Hamrle, Jaroslav (referee)
This work is dedicated to the study of two magnetic materials. Thin films of ferrimagnetic alloy GdxFe100−x fabricated with different compositions near the compensation temperature x . = 25 by magnetron sputtering on Si substrate with the usage of Ru and SiO2 capping layer were investigated. Measure- ments of the magneto-optic Kerr effect spectroscopy and magnetometry showed opposite signs in magnetization when the compensation temperature composi- tion exceeded as well as the enhancement of the effect for SiO2 capping layer. Spectroscopic ellipsometry revealed the complex diagonal element of the per- mittivity tensor. An attempt to prepare thin film of ferromagnetic tetragonal D022 − Mn3Ge was made. That was done firstly by calibrating Mn and Ge targets in magnetron sputtering machine and secondly simultaneous deposition of the elements on MgO (001) substrate with Cr buffer layer. 1
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Study of dynamically induced changes of magnetic properties in nanostructures
Ohnoutek, Lukáš ; Veis, Martin (advisor) ; Hamrle, Jaroslav (referee)
The aim of this bachelor thesis is the study of the changes of magnetic properties of the Co/GdOx interface under the influence of electric field. The main motivation is to identify the mechanism of the observed changes. Spectroscopic magneto-optic methods are used because of their high sensitivity and depth resolution. This makes them suitable for the study of the interface effects in thin multilayered structures. Two experimetal setups have been assembled to measure hysteresis loops and magneto-optical spectra of non-modified samples and voltage-modified samples. Measured magneto-optical spectra are compared to theoretical calculations of magneto-optic Kerr effect for the studied structure. The measurements together with the theoretical models prove that oxygen ions migrate from GdOx to Co under applied voltage.
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