• Bonda, Adam
• Uba, Luba
• Załęski, Karol
• Uba, Stanisław

Abstract

<p>The influence of the amplitude of an external magnetic field (H) and femtosecond laser pulse fluence (F) on ultrafast magnetization dynamics has been investigated in a ferromagnetic Ni54.3Mn31.9Sn13.8 Heusler-alloy film using the time-resolved magneto-optical Kerr effect. A large slowing down of the demagnetization process was observed and characteristic parameters of magnetization precession were determined for a wide range of H and F values. Long demagnetization times of the order of hundreds of picoseconds have been found and explained as a result of the Curie temperature (TC) proximity in the alloy film studied. Effective magnetic anisotropy field (Hkeff) and Gilbert damping parameter dependencies were determined. A significant reduction of the precession frequency versus F of the uniform Kittel mode was found. A strong decrease of Hkeff with F was well simulated in the frame of an extended version of the microscopic three-temperature model (eM3TM), and explained by the TC proximity effect. The estimated low values of the eM3TM model parameters, the demagnetization rate and electron-lattice coupling constant, appeared essential to explain the slowing down effect of demagnetization. Precession amplitude dependencies were explained by a phenomenological approach taking into account Hkeff and changes of the equilibrium magnetization angles induced by pump-pulse excitation.</p>

Topics

• magnetization
• Curie temperature