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Probing magnetic dynamics by soft X-ray scattering at a Free Electron Laser


Recently, we were able to exploit the potential of ultrafast resonant soft X-ray diffraction at the LCLS Free Electron Laser to uncover the melting of magnetic order in a manganite after vibrational excitation. Our experiments were carried out in the half-doped single-layer  La0.5Sr1.5MnO4 at the 640 eV Mn L-edge and reveal different time scales and amplitudes for magnetic and orbital order dynamics.

This effect is interpreted as a displacive exchange quench, a prompt shift in the equilibrium value of the magnetic- and orbital-order parameters after the lattice has been distorted. A microscopic description of this process is based on the ionic Raman scattering mechanism which leads to the excitation of a Jahn-Teller motion through lattice anharmonicities. 



Interaction with theoretical activities (Marzari group – MIT/Oxford/EPFL Lausanne) tackle this problem using ab-initio methods to simulate the response of the lattice to excitation of selective vibrational excitation and the coupling to other modes.


Experiment:



Related Publication:

Driving magnetic order in a manganite by ultrafast lattice excitation
M. Först, R. I. Tobey, S. Wall, H. Bromberger, V. Khanna, A. L. Cavalieri, Y.-D. Chuang, W. S. Lee, R. Moore, W. F. Schlotter, J. J. Turner, O. Krupin, M. Trigo, H. Zheng, J. F. Mitchell, S. S. Dhesi, J. P. Hill, and A. Cavalleri
Physical Review B 84, 241104(R)(2012)  
→ press release
 

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