The prospect of manipulating materials’ properties with femtosecond laser pulses, the shortest stimuli known to mankind, has fascinated researchers for decades. Discoveries of femtosecond demagnetization of ferromagnets and all-optical magnetic switching are fueled by the demand for faster information storage and processing. However, understanding when and how optical energy delivered into band electrons is transferred to spin and lattice degrees of freedom remains among the most challenging and important topics in condensed matter physics. Here we demonstrate for FePt nanoparticles how to disentangle these complex energy pathways. We show that femtosecond demagnetization launches a highly anisotropic ultrafast lattice motion characterized by a- and b-axis expansion and c-axis contraction. Picosecond lattice stress from non-equilibrium phonons increases the a,b-lattice spacing while invar-like near-zero c-axis expansion persists for tens of picoseconds. Our work establishes for a metallic system the existence of intimate spin, electron and lattice coupling, a hallmark usually reserved for strongly correlated electron systems.
Hermann A. Dürr, "Tracking the ultrafast spin-lattice motion in FePt nanoparticles
(Conference Presentation)," Proc. SPIE 9931, Spintronics IX, 993119 (Presented at SPIE Nanoscience + Engineering: August 29, 2016; Published: 4 November 2016); https://doi.org/10.1117/12.2239423.5166910704001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the conference proceedings. They include the speaker's narration along with a video recording of the presentation slides and animations. Many conference presentations also include full-text papers. Search and browse our growing collection of more than 12,000 conference presentations, including many plenary and keynote presentations.