Laser-induced precession of magnetization in ferrimagnetic GdFe thin films with low power excitation

We have investigated thermal effects on the dynamics of laser-induced precession of magnetization in ferrimagnetic GdFe thin films under low-excitation conditions (6-60 μJ/cm2). An increase in quasi-equilibrium temperature by laser heating causes a shift in precession frequency, which is explained analytically by the alteration of the magnetic anisotropy field by 2.2 [Oe] at a pulse fluence of 1 μJ/cm2. We have also demonstrated coherent control of the precession amplitude using a sequence of two laser pulses, each with a fluence of 18 μJ/cm2, and point out the importance of low-power excitation for precise control of the dynamic states.