Current understanding of the laser-induced ultrafast (de)magnetization process

The laser-induced ultrafast (de)magnetization process in ferromagnets is complex. There are several theories available [1], but none of these is satisfactory. In this talk, we first review several theoretical formalism for femtomagnetism and point out strengths and weaknesses of each theory [2]. In particular, we address issues associated with comparing experimental and theoretical results, which have been very challenging. Our first-principles theory includes electron correlation and electron-phonon effects along with spin-orbit coupling in metals or rare-earth compounds. Some of the newest results are presented, which are expected to tremendously enhance our understanding of the overall (de)magnetization process [3].\\[4pt] [1] G. P. Zhang, G. Lefkidis, W. H\"ubner, and Yihua Bai, J. APPL. PHYS. {\bf 111}, 07C508 (2012).\\[0pt] [2] M. S. Si and G. P. Zhang, AIP ADVANCES {\bf 2}, 012158 (2012).\\[0pt] [3] G. P. Zhang, PHYSICAL REVIEW B {\bf 85}, 224407 (2012).