Ultrafast magnetization dynamics of antiferromagnetic compounds Fiebig M., Duong N.P., Satoh T., Van Aken B.B., Miyano K., Tomioka Y., Tokura Y HISKP, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany; Max-Born-Institut, Max-Born-Strae 2A, 12489 Berlin, Germany; Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; ITIMS, Hanoi University of Technology, Dai Co Viet Road, Hanoi, Viet Nam; Institute of Industrial Science, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505, Japan; ECN, Solar Energy, PO Box 1, 1755 ZG Petten; RCAST, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904, Japan; Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan Abstract: In three different antiferromagnetic (AFM) materials we show that the magnetization dynamics of AFM compounds differs noticeably from that of ferromagnetic compounds Optical second harmonic generation and linear reflection were used to monitor with a temporal resolution of