由于磁存储和自旋电子学器件对速度的要求越来越高，磁动力学的研究在最近几十年是磁性材料研究的重点。最近发现采用飞秒激光脉冲可以使得磁性金属材料的磁矩在亚皮秒尺度退磁，提供了一种新的操纵自旋手段。尤其是在亚铁磁材料中发现超快的全光磁反转，导致飞秒磁学成为研究热点。通过研究反铁磁耦合对自旋角动量耗散的影响去寻找新的全光磁反转材料并，是研究全光磁反转的动力学机制以及未来全光磁反转器件发展的基础。本研究项目拟采用飞秒激光全光学泵浦探测的方法来研究亚铁磁FeCr合金薄膜中的超快退磁行为，重点是通过调节Cr的含量后，研究Fe-Cr间的反铁磁耦合对超快退磁的影响，来理解自旋角动量在亚铁磁次格子间的转移，并在FeCr合金薄膜中寻找到新的全光磁反转材料。

The study of magnetization dynamics has attracted a lot of attentions in the last two decades owing to the growing demands to increase the speed of controlling the magnetic state in magnetic recording media and spintronic devices. Recent experimental studies have revealed a new approach to manipulate the magnetization of magnetic materials on subpicosecond time scales by femtosecond laser pulses. More, a great deal of research has been dedicated to all-optical magnetization reversed materials in the past few years since its magnetization switching has been experimentally observed in subpicosecond time scale by femtosecond laser pulses. One of the prior work for understanding all-optical magnetization reversal and designing faster magnetic data-storage and spintronic devices based all-optical magnetization reversal is to seek new magnetic materials which can be all-optical magnetization reversed via exploring the correlation between the antiferromagnetic interaction of two sublattices and the disspation of spin angular momentum. This project will use an all optical pump-probe MOKE to probe the dynamics of the ultrafast demagnetization in FeCr alloy films. The antiferromagnetic interaction between Fe and Cr atoms can be tuned by varied content of Cr in ferrimagnetic FeCr films. Therefore we can explore the correlation between the ultrafast demagnetization and the antiferromagnetic interaction which is the key issue to understanding the spin angular momentum transfer between two sublattices.This work will help us to seek new magnetic materials which can be all-optical magnetization reversed among FeCr alloys.