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Investigation of magnetization dynamics in GaMnAs by ultrafast laser spectroscopy
Tesařová, Naďa ; Němec, Petr (advisor) ; Ferguson, Andrew (referee) ; Antoš, Roman (referee)
i Abstract: This doctoral thesis is dedicated to the study of magnetization dynamics in ferromagnetic semiconductor (Ga,Mn)As using magneto-optical (MO) spectroscopy methods. The character of the magnetization dynamics after the impact of the laser pulse was investigated under different experimental conditions in an extensive set of optimized (Ga,Mn)As samples with Mn doping ranging from 1.5% to 14%. The thorough analysis of the measured MO signal enabled us to develop a new method that can be used to determine the laser pulse-induced real-space magnetization trajectory without any numerical modelling. Moreover, the investigation of the measured MO signals allowed us to determine the basic micromagnetic properties of (Ga,Mn)As, such as the magnetic anisotropy, the Gilbert damping or the spin stiffness. In addition to this, we found out that the light-induced magnetization precession can be caused by three distinct mechanisms - the sample heating due to the energy transfer from the laser pulses, the angular momentum transfer from the circularly polarized photons, and the influence of the non-equilibrium hole polarization induced by the relativistic spin-orbit interaction. The first of these mechanisms is rather well known but the two remaining ones, which are the optical analogues of the spin-transfer torque...
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Investigation of magnetization dynamics in GaMnAs by ultrafast laser spectroscopy
Tesařová, Naďa ; Němec, Petr (advisor) ; Ferguson, Andrew (referee) ; Antoš, Roman (referee)
i Abstract: This doctoral thesis is dedicated to the study of magnetization dynamics in ferromagnetic semiconductor (Ga,Mn)As using magneto-optical (MO) spectroscopy methods. The character of the magnetization dynamics after the impact of the laser pulse was investigated under different experimental conditions in an extensive set of optimized (Ga,Mn)As samples with Mn doping ranging from 1.5% to 14%. The thorough analysis of the measured MO signal enabled us to develop a new method that can be used to determine the laser pulse-induced real-space magnetization trajectory without any numerical modelling. Moreover, the investigation of the measured MO signals allowed us to determine the basic micromagnetic properties of (Ga,Mn)As, such as the magnetic anisotropy, the Gilbert damping or the spin stiffness. In addition to this, we found out that the light-induced magnetization precession can be caused by three distinct mechanisms - the sample heating due to the energy transfer from the laser pulses, the angular momentum transfer from the circularly polarized photons, and the influence of the non-equilibrium hole polarization induced by the relativistic spin-orbit interaction. The first of these mechanisms is rather well known but the two remaining ones, which are the optical analogues of the spin-transfer torque...
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