William F. Schlotter, Xijie Wang, T. Vecchione, Pablo Maldonado, P. W. Granitzka, J. Cao, Yingchun Zhu, Karel Carva, Emmanuelle Jal, Nick Hartmann, Olav Hellwig, Xiaozhe Shen, Tianmin Liu, Alexander H. Reid, Ryan Coffee, Renkai Li, Eric E. Fullerton, Hendrik Ohldag, Liusuo Wu, Alan Fry, T. Chase, Jinpeng Wu, Georgi L. Dakovski, Zhao Chen, Virat Mehta, Hermann A. Dürr, Yukiko Takahashi, Daniel J. Higley, Jing Li, Peter M. Oppeneer, Joachim Stöhr, Department of Physics and Astronomy [Uppsala], Uppsala University, Chonnam National University [Gwangju], SLAC National Accelerator Laboratory (SLAC), Stanford University, HGST San Jose Research Center, Imagerie et modélisation Vasculaires, Thoraciques et Cérébrales (MOTIVATE), Centre de Recherche en Acquisition et Traitement de l'Image pour la Santé (CREATIS), Université Jean Monnet [Saint-Étienne] (UJM)-Hospices Civils de Lyon (HCL)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Jean Monnet [Saint-Étienne] (UJM)-Hospices Civils de Lyon (HCL)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM), Center for Magnetic Recording Research, University of California [San Diego] (UC San Diego), University of California-University of California, College of Materials Science and Optoelectronic Technology, and University of Chinese Academy Sciences more...
Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction—the underlying magnetoelastic stress—can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization., Although magnetostriction is universal in magnetic materials, understanding its microscopic origin remains challenging. Here the authors use X-ray and ultrafast electron diffraction to separate the material’s sub-picosecond spin and lattice responses and reveal the magnetoelastic stress generated by demagnetization. more...