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Vliv pnutí na magnetooptické vlasnosti La2/3Sr1/3MnO3
Maleček, Tomáš ; Veis, Martin (advisor) ; Verhagen, Timotheus Guillaume Albertus (referee)
The influence of epitaxial strain on La2/3Sr1/3MnO3 (LSMO) thin films has been studied by magneto-optical spectroscopy. The investigated samples have been grown by pulsed laser deposition on four different substrates with varying degree of compressive and tensile strain. The spectra of the magneto-optical Kerr effect (MOKE) have been measured. Deterioration of magnetic properties with increasing epitaxial strain has been observed. The off-diagonal elements of the permittivity tensor, numerically calculated from the MOKE and spectroscopic ellipsometry measurements, confirmed two already reported electronic transitions. A third transition at around 4.3 eV has been observed on samples grown under compressive strain. The dependence of the Kerr rotation spectra on temperature has been measured for all four samples. The Curie temperatures have been estimated for all samples with the exception of LSMO grown on LaAlO3 which undergoes a spin reorientation transition at 200 K. The low temperature measurements on the compressively strained samples showed amplification of the third transition supporting the claim of it being paramagnetic. Also observed was a change in the spectra of the Kerr rotation of the sample grown on SrTiO3 which undergoes a structural transition at 105 K, and, therefore, changes the epitaxial strain.
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Vliv pnutí na magnetooptické vlasnosti La2/3Sr1/3MnO3
Maleček, Tomáš ; Veis, Martin (advisor) ; Verhagen, Timotheus Guillaume Albertus (referee)
The influence of epitaxial strain on La2/3Sr1/3MnO3 (LSMO) thin films has been studied by magneto-optical spectroscopy. The investigated samples have been grown by pulsed laser deposition on four different substrates with varying degree of compressive and tensile strain. The spectra of the magneto-optical Kerr effect (MOKE) have been measured. Deterioration of magnetic properties with increasing epitaxial strain has been observed. The off-diagonal elements of the permittivity tensor, numerically calculated from the MOKE and spectroscopic ellipsometry measurements, confirmed two already reported electronic transitions. A third transition at around 4.3 eV has been observed on samples grown under compressive strain. The dependence of the Kerr rotation spectra on temperature has been measured for all four samples. The Curie temperatures have been estimated for all samples with the exception of LSMO grown on LaAlO3 which undergoes a spin reorientation transition at 200 K. The low temperature measurements on the compressively strained samples showed amplification of the third transition supporting the claim of it being paramagnetic. Also observed was a change in the spectra of the Kerr rotation of the sample grown on SrTiO3 which undergoes a structural transition at 105 K, and, therefore, changes the epitaxial strain.
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Dynamic control of magnetization for spintronic applications studied by magneto-optical methods
Zahradník, Martin ; Veis, Martin (advisor) ; Herranz, Gervasi (referee) ; Legut, Dominik (referee)
Two important mechanisms in preparation of ultrathin films of magnetic oxides were systematically investigated in this work. First, influence of epitaxial strain on resulting magneto-optical properties of La2/3Sr1/3MnO3 (LSMO) ultrathin films was studied. The investigated films were grown by pulsed laser deposition on four different substrates, providing a broad range of induced epitaxial strains. Magnetic properties were found to deteriorate with increasing value of the epitaxial strain, as expected due to the unit cell distortion increasingly deviating from the bulk and effect of the magnetically inert layer. A combination of spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy was used to determine spectra of the diagonal and off-diagonal elements of permittivity tensor. The off-diagonal elements confirmed presence of two previously reported electronic transitions in spectra of all films. Moreover, they revealed another electronic transition around 4.3 eV only in spectra of films grown under compressive strain. We proposed classification of this transition as crystal field paramagnetic Mn t2g → eg transition, which was further supported by ab initio calculations. A key role of strain in controlling electronic structure of ultrathin perovskite films was demonstrated. Dynamic application of...
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