Enhanced inertial magnetization response driven by chirped terahertz field

We explore the spin dynamics process in ferromagnets driven by chirped THz fields, utilizing the spin dynamics model derived from the inertial Landau-Lifshitz-Gilbert equation. Our findings reveal a substantial enhancement in spin dynamics intensity, ranging from 15% to 20% when the sample is subjected to a chirped THz pulse. Additionally, it is observed that chirped THz fields have the capability to shift the peak of spin dynamics, with the variation dependent on the chirping time of the THz pulse. Furthermore, the underlying physical mechanisms responsible for such spin dynamics are well explained by the Zeeman torque and the time delay of different frequencies of the chirped THz fields within the framework of the inertial Landau-Lifshitz-Gilbert equation.