Ultrafast and Distinct Spin Dynamics in Magnetic Alloys

Controlling magnetic order on ultrashort timescales is crucial for engineering the next-generation magnetic devices that combine ultrafast data processing with ultrahigh-density data storage. An appealing scenario in this context is the use of femtosecond (fs) laser pulses as an ultrafast, external stimulus to fully set the orientation and the magnetization magnitude of a spin ensemble. Achieving such control on ultrashort timescales, e.g., comparable to the excitation event itself, remains however a challenge due to the lack of understanding the dynamical behavior of the key parameters governing magnetism; the elemental magnetic moments and the exchange interaction.

Screen Shot 2015-08-21 at 11.13.08In a new article published in the journal SPIN, we investigate the fs laser-induced spin dynamics in a variety of multi-component alloys and reveal a dissimilar dynamics of the constituent magnetic moments on ultrashort timescales. Moreover, we show that such distinct dynamics is a general phenomenon that can be exploited to engineer new magnetic media with tailor-made, optimized dynamic properties. Using phenomenological considerations, atomistic modeling and time-resolved X-ray magnetic circular dichroism (XMCD), we demonstrate demagnetization of the constituent sub-lattices on significantly different timescales that depend on their magnetic moments and the sign of the exchange interaction. The results can be used as a “recipe” for manipulation and control of magnetization dynamics in a large class of magnetic materials.

Cover for issue 3 of volume 5 of the SPIN journal
Cover for issue 3 of volume 5 of the SPIN journal

This work was lead by Ilie Radu (TU Berlin) and carried out in collaboration with a number of experimental and theoretical partners across Europe and Japan. The article is made publicly available through the journal’s open access format and was selected as the front cover highlight of the issue (see image above) and was in the top five most downloaded articles in 2015 in the journal SPIN. The work would not have been possible without the support of the European Community’s Seventh Framework Program (FP7/2007–2013) Grants No. NMP3-SL-2008-214469 (UltraMagnetron), No. 214810 (FANTOMAS) and No. 281043 (FEMTOSPIN) and ERC Grant No. 257280 (Femtomagnetism) as well as Grant No. 226716 and ERC-2013- AdG339813-EXCHANGE, the German Federal Ministry of Education and Research (BMBF) Grant No. 05K10PG2 (FEMTOSPEX), the Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization for Scientic Research (NWO) is gratefully acknowledged.