|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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...
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
guest ::
