Mater. Res. Soc. Symp. Proc. Vol. 1528 © 2013 Materials Research Society DOI: 1 557/op 013 0.1 l.2 . Ultrafast Photostriction in Thin Film Bismuth Ferrite and its Correlation to Electronic Dynamics Yuelin Li 1* , Haidan Wen 1 , Pice Chen 2 , Margaret P. Cosgriff 2 , Donald Walko 1 , June Hyuk Lee 1 , Carolina Adamo 3 , Richard Schaller 4,5 , Clare Rowland 5 , Christian Schlepuetz 1 , Eric Dufresne 1 , Qingteng Zhang 2 , Carlos Giles, 6 , Darrell Schlom 3 , John Freeland 1 , and Paul Evans 2 1 X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA 2 Department of Materials Science and Engineering and Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA 3 Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501, USA 4 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, USA 5 Department of Chemistry, Northwestern University, Evanston, IL 60208, USA 6 Universidade Estadual de Campinas, 13083-859 Campinas, SP, Brazil *ylli@aps.anl.gov ABSTRACT A series of laser pump, x-ray probe experiments show that above band gap photoexcitation can generate a large out-of-plane strain in multiferroic BiFeO 3 thin films. The strain decays in a time scale that is the same as the photo-induced carriers measured in an optical transient absorption spectroscopy experiment. We attribute the strain to the piezoelectric effect due to screening of the depolarization field by laser induced carriers. A strong film thickness dependence of strain and carrier relaxation is also observed, revealing the role of the carrier transport in determining the structural and carrier dynamics in complex oxide thin films. INTRODUCTION Ultrafast lattice dynamics in an epitaxial thin film of the room-temperature multiferroic bismuth ferrite can be driven by ultrafast laser-generated photocarriers. We report a structural study of these dynamics with a temporal resolution of 100 ps. Multiferroics exhibit simultaneous magnetic and ferroelectric (FE) degrees of freedom [1, 2]. The coupling between these degrees of freedom and their interaction with mechanical and optical excitations is beginning to be understood under static conditions [3, 4], but the timescales of the interaction of polarization and 396