The angular dependence of magnetization dynamics induced by a GHz range strain pulse

The dynamics of magnetization is important in spintronics, where the coupling between phonon and magnon attracts much attention. In this work, we study the angular dependence of the coupling between longitudinal-wave phonon and magnon. We investigated the magnetization dynamics using the time-resolved magneto-optical Kerr effect, which allows measuring spin-wave resonances and the magnetic echo signal. The frequency, mode number, and amplitude of the spin-wave resonance change with the out-of-plane angle of the external magnetic field. The amplitude of the magnetic echo signal caused by the strain pulse also changes with the angle. We calculate these angular dependences based on the Landau-Lifshitz-Gilbert equation and find that the angles of the external field and magnetic moment are important factors for the phonon-magnon coupling when phonon propagates in the thickness direction under the out-of-plane magnetic field.

Femtosecond Pump-Probe Investigation of Ultrafast Phenomenon of GaAs

The effect process between femtosecond laser and matter had been introduced first. Then introduce the theory of strain pulse and the experiment set up.We detect transient reflectivity change on surface of GaAs at different delayed time using femtosecond transient reflection spectroscopy.We found it was made up of three parts: original scattering process of 100fs, carriers-lattice thermal equilibrium of 1.5ps and recombination process of 500ps.