Journal of East China Normal University(Natural Sc ›› 2018, Vol. 2018 ›› Issue (2): 109-114.doi: 10.3969/j.issn.1000-5641.2018.02.011

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Coherent acoustic phonon inmagnetic thin films excited by femtosecond laser

YAN Jia-qi, LI Wei, LOU Shi-tao, ZHANG Xiao-lei   

  1. State Key Laboratory of Precision Spectroscopy Science and Technology, East China Normal University, Shanghai 200062, China
  • Received:2017-04-19 Online:2018-03-25 Published:2018-03-22

Abstract: The interaction between the femtosecond laser pulse and the MnIr layer in the magnetic thin film excites the coherent acoustic phonon with an initial phase of 90° and a propagation velocity of 4 300 m/s. The vibration frequency of the acoustic phonon is independent of the laser energy density and is inversely proportional to the total thickness of the magnetic thin film. And the acoustic phono can propagate in the adjacent metal layers due to the high lattice matching. The electron temperature in the magnetic thin film increases sharply absorbing by femtosecond laser pulse, then an decreasing electron temperature gradient with increasing depth is generated instantaneously by the absorption of the laser which lead to the lattice oscillate coherently in the depth direction, that is, the acoustic phonon. In addition, the frequency of the acoustic phonon changes caused by the applied magnetic field is within the experimental error range, indicating that the magnetic interaction is very weak compared to the electrical interaction in the lattice.

Key words: femtosecond laser, coherent acoustic phonon, pump-probe, magnetic film

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