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Studium fyzikálních vlastostí magnetických oxidů spektroskopickými metodami
Zahradník, Martin ; Veis, Martin (advisor) ; Kouřil, Karel (referee)
Two groups of magnetic oxides were investigated in this thesis. Thin films of La2/3Sr1/3MnO3 (LSMO) deposited by pulsed laser deposition (PLD) on SrTiO3 (STO) substrates were characterized by polar and longitudinal magneto-optical (MO) Kerr spectroscopy. Experimental results were compared to theoretical calculations based on the transfer matrix formalism. A very good agreement between experimental and theoretical data revealed high magnetic ordering down to 5 nm of film thickness as well as a mechanism of suppression of double exchange interaction near the LSMO/STO interface. Magnetically doped Ce1-xCoxO2-δ films deposited by PLD on MgO (x = 0.05 and 0.10) and oxidized Si (x = 0.20) substrates were studied by combination of spectroscopic ellipsometry and MO Faraday and Kerr spectroscopy. Both diagonal and off-diagonal permittivity tensor components were obtained and verified by theoretical calculations confronted with experimental data. Diagonal spectra revealed two optical transitions from oxygen to cerium states. Off-diagonal spectra revealed two paramagnetic transitions involving cobalt ions. An essential influence of cobalt doping on the resulting ferromagnetic properties of CeO2 was observed.
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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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Magnetooptical spectroscopy of La2/3Sr1/3MnO3 ultrathin films
Zahradník, Martin ; Veis, Martin (advisor) ; Postava, Kamil (referee)
High quality La2/3Sr1/3MnO3 (LSMO) ultrathin layers are of interest for applications in magnetic sensors and spintronic devices due to colossal magnetoresistance of these materials. LSMO films studied in this thesis were grown by pulsed laser deposition on SrTiO3 substrates. The deposition at low oxygen pressures with the use of a beam homogenizer leads to the high quality LSMO films. The film thickness ranges from 5,0 to 103,9 nm. Magnetooptical (MO) spectrometer based on azimuth modulation was used and spectra of MO Kerr effect in polar and longitudinal configuration were obtained. All the spectra display features typical for LSMO films, including the thinnest 5 nm thick film. MO Kerr effect observed in this film reflects high magnetic ordering even at such low thickness. All the spectra manifest high quality of the LSMO films prepared with the use of the beam homogenizer.
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Studium fyzikálních vlastností magnetických oxidů spektroskopickými metodami
Zahradník, Martin ; Veis, Martin (advisor)
Two groups of magnetic oxides were investigated in this thesis. Thin films of La2/3Sr1/3MnO3 (LSMO) deposited by pulsed laser deposition (PLD) on SrTiO3 (STO) substrates were characterized by polar and longitudinal magneto-optical (MO) Kerr spectroscopy. Experimental results were compared to theoretical calculations based on the transfer matrix formalism. A very good agreement between experimental and theoretical data revealed high magnetic ordering down to 5 nm of film thickness as well as a mechanism of suppression of double exchange interaction near the LSMO/STO interface. Magnetically doped Ce1-xCoxO2-δ films deposited by PLD on MgO (x = 0.05 and 0.10) and oxidized Si (x = 0.20) substrates were studied by combination of spectroscopic ellipsometry and MO Faraday and Kerr spectroscopy. Both diagonal and off-diagonal permittivity tensor components were obtained and verified by theoretical calculations confronted with experimental data. Diagonal spectra revealed two optical transitions from oxygen to cerium states. Off-diagonal spectra revealed two paramagnetic transitions involving cobalt ions. An essential influence of cobalt doping on the resulting ferromagnetic properties of CeO2 was observed.
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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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Studium fyzikálních vlastností magnetických oxidů spektroskopickými metodami
Zahradník, Martin ; Veis, Martin (advisor)
Two groups of magnetic oxides were investigated in this thesis. Thin films of La2/3Sr1/3MnO3 (LSMO) deposited by pulsed laser deposition (PLD) on SrTiO3 (STO) substrates were characterized by polar and longitudinal magneto-optical (MO) Kerr spectroscopy. Experimental results were compared to theoretical calculations based on the transfer matrix formalism. A very good agreement between experimental and theoretical data revealed high magnetic ordering down to 5 nm of film thickness as well as a mechanism of suppression of double exchange interaction near the LSMO/STO interface. Magnetically doped Ce1-xCoxO2-δ films deposited by PLD on MgO (x = 0.05 and 0.10) and oxidized Si (x = 0.20) substrates were studied by combination of spectroscopic ellipsometry and MO Faraday and Kerr spectroscopy. Both diagonal and off-diagonal permittivity tensor components were obtained and verified by theoretical calculations confronted with experimental data. Diagonal spectra revealed two optical transitions from oxygen to cerium states. Off-diagonal spectra revealed two paramagnetic transitions involving cobalt ions. An essential influence of cobalt doping on the resulting ferromagnetic properties of CeO2 was observed.
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Studium fyzikálních vlastostí magnetických oxidů spektroskopickými metodami
Zahradník, Martin ; Veis, Martin (advisor) ; Kouřil, Karel (referee)
Two groups of magnetic oxides were investigated in this thesis. Thin films of La2/3Sr1/3MnO3 (LSMO) deposited by pulsed laser deposition (PLD) on SrTiO3 (STO) substrates were characterized by polar and longitudinal magneto-optical (MO) Kerr spectroscopy. Experimental results were compared to theoretical calculations based on the transfer matrix formalism. A very good agreement between experimental and theoretical data revealed high magnetic ordering down to 5 nm of film thickness as well as a mechanism of suppression of double exchange interaction near the LSMO/STO interface. Magnetically doped Ce1-xCoxO2-δ films deposited by PLD on MgO (x = 0.05 and 0.10) and oxidized Si (x = 0.20) substrates were studied by combination of spectroscopic ellipsometry and MO Faraday and Kerr spectroscopy. Both diagonal and off-diagonal permittivity tensor components were obtained and verified by theoretical calculations confronted with experimental data. Diagonal spectra revealed two optical transitions from oxygen to cerium states. Off-diagonal spectra revealed two paramagnetic transitions involving cobalt ions. An essential influence of cobalt doping on the resulting ferromagnetic properties of CeO2 was observed.
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Magnetooptical spectroscopy of La2/3Sr1/3MnO3 ultrathin films
Zahradník, Martin ; Veis, Martin (advisor) ; Postava, Kamil (referee)
High quality La2/3Sr1/3MnO3 (LSMO) ultrathin layers are of interest for applications in magnetic sensors and spintronic devices due to colossal magnetoresistance of these materials. LSMO films studied in this thesis were grown by pulsed laser deposition on SrTiO3 substrates. The deposition at low oxygen pressures with the use of a beam homogenizer leads to the high quality LSMO films. The film thickness ranges from 5,0 to 103,9 nm. Magnetooptical (MO) spectrometer based on azimuth modulation was used and spectra of MO Kerr effect in polar and longitudinal configuration were obtained. All the spectra display features typical for LSMO films, including the thinnest 5 nm thick film. MO Kerr effect observed in this film reflects high magnetic ordering even at such low thickness. All the spectra manifest high quality of the LSMO films prepared with the use of the beam homogenizer.
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