Distinguishing Local and non-Local Demagnetization in Ferromagnetic FePt Nanoparticles
Abstract
Time-resolved coherent X-ray diffraction is used to measure the spatially resolved magnetization structure within FePt nanoparticles during laser-induced ultrafast demagnetization. The momentum-dependent X-ray magnetic diffraction shows that demagnetization proceeds at different rates at different X-ray momentum transfer. We show that the observed momentum-dependent scattering has the signature of inhomogeneous demagnetization within the nanoparticles, with the demagnetization proceeding more rapidly at the boundary of the nanoparticle. A shell region of reduced magnetization forms and moves inwards at a supermagnonic velocity. Spin-transport calculations show that the shell formation is driven by superdiffusive spin flux mainly leaving the nanoparticle into the surrounding carbon. Quantifying this non-local contribution to the demagnetization allows us to separate it from the local demagnetization.
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Cite
@article{arxiv.1903.08287,
title = {Distinguishing Local and non-Local Demagnetization in Ferromagnetic FePt Nanoparticles},
author = {Patrick W. Granitzka and Alexander H. Reid and Jerome Hurst and Emmanuelle Jal and Loïc Le Guyader and Tian-Min Liu and Leandro Salemi and Daniel J. Higley and Tyler Chase and Zhao Chen and Marco Berritta and William F. Schlotter and Hendrik Ohldag and Georgi L. Dakovski and Sebastian Carron and Matthias C. Hoffmann and Jian Wang and Virat Mehta and Olav Hellwig and Eric E. Fullerton and Yukiko K. Takahashi and Joachim Stöhr and Peter M. Oppeneer and Hermann A. Dürr},
journal= {arXiv preprint arXiv:1903.08287},
year = {2019}
}
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6 pages