Synchronized time- and high-field-resolved all-optical pump-probe magneto-optical setup based on a strong alternating magnetic field and its application in magnetization dynamics of high coercivity magnetic medium.

An alternating magnetic field (AMF) apparatus is developed and composed of an electromagnet and driving power supply. The structure of the electromagnet and configuration of the driving supply are described in detail. The apparatus can produce a peak magnetic field up to 9000 Oe and above under a small driving power at its resonance frequency of 1.14 kHz. Based on synchronization between the AMF and the femtosecond laser pulse train, a photomagnetic synchronized time- and high-field-resolved all-optical pump-probe magnetic-optical setup is developed. This setup has the ability to reinitialize any magnetic states between two successive laser pulses so that irreversible magnetization reversal dynamics can be studied. Dynamic Kerr hysteresis loops and magnetization reversal dynamics of high coercivity ferromagnetic TbFeCo and FePt films are demonstrated using this setup, showing importance of this synchronized time- and high-field-resolved all-optical pump-probe magnetic-optical setup in the research of ultrafast magnetization dynamics.